The International Human Dimensions Programme on Global Environmental Change ( IHDP ) was a research programme that studied the human and societal aspects of the phenomenon of global change .
111-470: IHDP aimed to frame, develop and integrate social science research on global change, and promote the application of its key findings. It strived to develop research approaches that put societies at the center of the debate, looking at then-current global environmental problems as social and societal challenges. IHDP’s work brought together groups of multi-disciplinary and multi-national researchers to work on long-term collaborative science. Its former role within
222-662: A 25% increase in global annual dust emissions between the late nineteenth century to present day. The increase of desertification has also increased the amount of loose sand and dust that the wind can pick up ultimately resulting in a storm. For example, dust storms in the Middle East “are becoming more frequent and intense in recent years” because “long-term reductions in rainfall [cause] lower soil moisture and vegetative cover ”. Dust storms can contribute to certain respiratory disorders such as pneumonia, skin irritations, asthma and many more. They can pollute open water, reduce
333-562: A broader sense also includes previous long-term changes to Earth's climate. The current rise in global temperatures is driven by human activities , especially fossil fuel burning since the Industrial Revolution . Fossil fuel use, deforestation , and some agricultural and industrial practices release greenhouse gases . These gases absorb some of the heat that the Earth radiates after it warms from sunlight , warming
444-590: A decadal timescale. Other changes are caused by an imbalance of energy from external forcings . Examples of these include changes in the concentrations of greenhouse gases , solar luminosity , volcanic eruptions, and variations in the Earth's orbit around the Sun. To determine the human contribution to climate change, unique "fingerprints" for all potential causes are developed and compared with both observed patterns and known internal climate variability . For example, solar forcing—whose fingerprint involves warming
555-542: A lot of light to being dark after the ice has melted, they start absorbing more heat . Local black carbon deposits on snow and ice also contribute to Arctic warming. Arctic surface temperatures are increasing between three and four times faster than in the rest of the world. Melting of ice sheets near the poles weakens both the Atlantic and the Antarctic limb of thermohaline circulation , which further changes
666-419: A major role in determining the biological composition of the soil , studies have shown that, in many environments, the rate of erosion and runoff decreases exponentially with increased vegetation cover. Unprotected, dry soil surfaces blow away with the wind or are washed away by flash floods, leaving infertile lower soil layers that bake in the sun and become an unproductive hardpan. Early studies argued one of
777-416: A major role in determining the biological composition of the soil , studies have shown that, in many environments, the rate of erosion and runoff decreases exponentially with increased vegetation cover. Unprotected, dry soil surfaces blow away with the wind or are washed away by flash floods, leaving infertile lower soil layers that bake in the sun and become an unproductive hardpan. This spread of arid areas
888-412: A marked increase in temperature. Ongoing changes in climate have had no precedent for several thousand years. Multiple independent datasets all show worldwide increases in surface temperature, at a rate of around 0.2 °C per decade. The 2014–2023 decade warmed to an average 1.19 °C [1.06–1.30 °C] compared to the pre-industrial baseline (1850–1900). Not every single year was warmer than
999-408: A physical climate model. These models simulate how population, economic growth , and energy use affect—and interact with—the physical climate. With this information, these models can produce scenarios of future greenhouse gas emissions. This is then used as input for physical climate models and carbon cycle models to predict how atmospheric concentrations of greenhouse gases might change. Depending on
1110-437: A probable increase from 14 million in 2010 to nearly 200 million by 2050. This presents a future crisis for the region, as neighboring nations do not always have the ability to support large populations of refugees. In Mongolia , the land is 90% fragile dry land, which causes many herders to migrate to the city for work. With very limited resources, the herders that stay on the dry land graze very carefully in order to preserve
1221-461: A result of climate change. Global sea level is rising as a consequence of thermal expansion and the melting of glaciers and ice sheets . Sea level rise has increased over time, reaching 4.8 cm per decade between 2014 and 2023. Over the 21st century, the IPCC projects 32–62 cm of sea level rise under a low emission scenario, 44–76 cm under an intermediate one and 65–101 cm under
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#17327985460011332-498: A result, changing ocean temperature and reductions in sulfate emissions have caused a re-greening of the region. This has led some scholars to argue that agriculture-induced vegetation loss is a minor factor in desertification. Human population dynamics have a considerable impact on overgrazing, over-farming and deforestation, as previously acceptable techniques have become unsustainable. There are multiple reasons farmers use intensive farming as opposed to extensive farming but
1443-474: A result. The World Health Organization calls climate change one of the biggest threats to global health in the 21st century. Societies and ecosystems will experience more severe risks without action to limit warming . Adapting to climate change through efforts like flood control measures or drought-resistant crops partially reduces climate change risks, although some limits to adaptation have already been reached. Poorer communities are responsible for
1554-417: A small share of global emissions , yet have the least ability to adapt and are most vulnerable to climate change . Many climate change impacts have been observed in the first decades of the 21st century, with 2023 the warmest on record at +1.48 °C (2.66 °F) since regular tracking began in 1850. Additional warming will increase these impacts and can trigger tipping points , such as melting all of
1665-548: A very high emission scenario. Marine ice sheet instability processes in Antarctica may add substantially to these values, including the possibility of a 2-meter sea level rise by 2100 under high emissions. Climate change has led to decades of shrinking and thinning of the Arctic sea ice . While ice-free summers are expected to be rare at 1.5 °C degrees of warming, they are set to occur once every three to ten years at
1776-519: A warming level of 2 °C. Higher atmospheric CO 2 concentrations cause more CO 2 to dissolve in the oceans, which is making them more acidic . Because oxygen is less soluble in warmer water, its concentrations in the ocean are decreasing , and dead zones are expanding. Greater degrees of global warming increase the risk of passing through ' tipping points '—thresholds beyond which certain major impacts can no longer be avoided even if temperatures return to their previous state. For instance,
1887-455: Is a lack of political will, and lack of funding to support land reclamation and anti-desertification programs. Desertification is recognized as a major threat to biodiversity . Some countries have developed biodiversity action plans to counter its effects, particularly in relation to the protection of endangered flora and fauna . Techniques focus on two aspects: provisioning of water, and fixation and hyper-fertilizing soil. Fixating
1998-430: Is a type of gradual land degradation of fertile land into arid desert due to a combination of natural processes and human activities. The immediate cause of desertification is the loss of most vegetation. This is driven by a number of factors, alone or in combination, such as drought, climatic shifts, tillage for agriculture, overgrazing and deforestation for fuel or construction materials. Though vegetation plays
2109-564: Is an estimated total sea level rise of 2.3 metres per degree Celsius (4.2 ft/°F) after 2000 years. Oceanic CO 2 uptake is slow enough that ocean acidification will also continue for hundreds to thousands of years. Deep oceans (below 2,000 metres (6,600 ft)) are also already committed to losing over 10% of their dissolved oxygen by the warming which occurred to date. Further, the West Antarctic ice sheet appears committed to practically irreversible melting, which would increase
2220-420: Is caused by a variety of factors, such as overexploitation of soil as a result of human activity and the effects of climate change . At least 90% of the inhabitants of drylands live in developing countries , where they also suffer from poor economic and social conditions. This situation is exacerbated by land degradation because of the reduction in productivity, the precariousness of living conditions and
2331-711: Is determined by modelling the carbon cycle and climate sensitivity to greenhouse gases. According to UNEP , global warming can be kept below 1.5 °C with a 50% chance if emissions after 2023 do not exceed 200 gigatonnes of CO 2 . This corresponds to around 4 years of current emissions. To stay under 2.0 °C, the carbon budget is 900 gigatonnes of CO 2 , or 16 years of current emissions. The climate system experiences various cycles on its own which can last for years, decades or even centuries. For example, El Niño events cause short-term spikes in surface temperature while La Niña events cause short term cooling. Their relative frequency can affect global temperature trends on
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#17327985460012442-399: Is independent of where greenhouse gases are emitted, because the gases persist long enough to diffuse across the planet. Since the pre-industrial period, the average surface temperature over land regions has increased almost twice as fast as the global average surface temperature. This is because oceans lose more heat by evaporation and oceans can store a lot of heat . The thermal energy in
2553-458: Is mostly due to the climate conditions before the growing season, which influence the rate of evapotranspiration and subsequent plant growth. The expansion of the Gobi is attributed mostly to human activities, locally driven by deforestation , overgrazing , and depletion of water resources, as well as to climate change . South America is another area vulnerable by desertification, as 25% of
2664-418: Is no single metric which can define all aspects. However, more intense climate change is still expected to increase the current extent of drylands on the Earth's continents: from 38% in late 20th century to 50% or 56% by the end of the century, under the "moderate" and high-warming Representative Concentration Pathways 4.5 and 8.5. Most of the expansion will be seen over regions such as "southwest North America,
2775-450: Is primarily attributed to sulfate aerosols produced by the combustion of fossil fuels with heavy sulfur concentrations like coal and bunker fuel . Smaller contributions come from black carbon (from combustion of fossil fuels and biomass), and from dust. Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much. Aerosols also have indirect effects on
2886-444: Is radiating into space. Warming reduces average snow cover and forces the retreat of glaciers . At the same time, warming also causes greater evaporation from the oceans , leading to more atmospheric humidity , more and heavier precipitation . Plants are flowering earlier in spring, and thousands of animal species have been permanently moving to cooler areas. Different regions of the world warm at different rates . The pattern
2997-516: Is shaped by feedbacks, which either amplify or dampen the change. Self-reinforcing or positive feedbacks increase the response, while balancing or negative feedbacks reduce it. The main reinforcing feedbacks are the water-vapour feedback , the ice–albedo feedback , and the net effect of clouds. The primary balancing mechanism is radiative cooling , as Earth's surface gives off more heat to space in response to rising temperature. In addition to temperature feedbacks, there are feedbacks in
3108-562: Is still considered to be at risk of disappearing entirely. To limit desertification, the Great Green Wall (Africa) initiative was started in 2007 involving the planting of vegetation along a stretch of 7,775 km, 15 km wide, involving 22 countries to 2030. The purpose of this mammoth planting initiative is to enhance retention of water in the ground following the seasonal rainfall, thus promoting land rehabilitation and future agriculture. Senegal has already contributed to
3219-407: Is the major reason why different climate models project different magnitudes of warming for a given amount of emissions. A climate model is a representation of the physical, chemical and biological processes that affect the climate system. Models include natural processes like changes in the Earth's orbit, historical changes in the Sun's activity, and volcanic forcing. Models are used to estimate
3330-453: Is through the use of nitrogen-rich fertilizer. Due to the higher cost of this fertilizer, many smallholder farmers are reluctant to use it, especially in areas where subsistence farming is common. Several nations, including India, Zambia, and Malawi have responded to this by implementing subsidies to help encourage adoption of this technique. Some research centres (such as Bel-Air Research Center IRD/ISRA/UCAD) are also experimenting with
3441-417: Is unclear. A related phenomenon driven by climate change is woody plant encroachment , affecting up to 500 million hectares globally. Climate change has contributed to the expansion of drier climate zones, such as the expansion of deserts in the subtropics . The size and speed of global warming is making abrupt changes in ecosystems more likely. Overall, it is expected that climate change will result in
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3552-411: Is useful is contour trenching . This involves the digging of 150 m long, 1 m deep trenches in the soil. The trenches are made parallel to the height lines of the landscape, preventing the water from flowing within the trenches and causing erosion. Stone walls are placed around the trenches to prevent the trenches from closing up again. This method was invented by Peter Westerveld. Enriching of
3663-511: The Atlantic meridional overturning circulation (AMOC), and irreversible damage to key ecosystems like the Amazon rainforest and coral reefs can unfold in a matter of decades. The long-term effects of climate change on oceans include further ice melt, ocean warming , sea level rise, ocean acidification and ocean deoxygenation. The timescale of long-term impacts are centuries to millennia due to CO 2 's long atmospheric lifetime. The result
3774-661: The Earth's energy budget . Sulfate aerosols act as cloud condensation nuclei and lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets. They also reduce the growth of raindrops , which makes clouds more reflective to incoming sunlight. Indirect effects of aerosols are the largest uncertainty in radiative forcing . While aerosols typically limit global warming by reflecting sunlight, black carbon in soot that falls on snow or ice can contribute to global warming. Not only does this increase
3885-573: The Greenland ice sheet is already melting, but if global warming reaches levels between 1.7 °C and 2.3 °C, its melting will continue until it fully disappears. If the warming is later reduced to 1.5 °C or less, it will still lose a lot more ice than if the warming was never allowed to reach the threshold in the first place. While the ice sheets would melt over millennia, other tipping points would occur faster and give societies less time to respond. The collapse of major ocean currents like
3996-840: The Greenland ice sheet . Under the 2015 Paris Agreement , nations collectively agreed to keep warming "well under 2 °C". However, with pledges made under the Agreement, global warming would still reach about 2.8 °C (5.0 °F) by the end of the century. Limiting warming to 1.5 °C would require halving emissions by 2030 and achieving net-zero emissions by 2050. Fossil fuel use can be phased out by conserving energy and switching to energy sources that do not produce significant carbon pollution. These energy sources include wind , solar , hydro , and nuclear power . Cleanly generated electricity can replace fossil fuels for powering transportation , heating buildings , and running industrial processes. Carbon can also be removed from
4107-635: The Industrial Revolution , naturally-occurring amounts of greenhouse gases caused the air near the surface to be about 33 °C warmer than it would have been in their absence. Human activity since the Industrial Revolution, mainly extracting and burning fossil fuels ( coal , oil , and natural gas ), has increased the amount of greenhouse gases in the atmosphere. In 2022, the concentrations of CO 2 and methane had increased by about 50% and 164%, respectively, since 1750. These CO 2 levels are higher than they have been at any time during
4218-639: The International Social Science Council (ISSC). It was established under its closing name International Human Dimensions Programme on Global Environmental Change by ISSC and International Council for Science (ICSU) in 1996. In 2006, the United Nations University joined ISSC and ICSU as an institutional sponsor of IHDP. The organization closed its doors in July 2014. A large part of the research agenda of
4329-899: The North African climate cycle that alters the path of the North African Monsoon , caused by an approximately 40,000-year cycle in which the axial tilt of the earth changes between 22° and 24.5°). Some statistics have shown that, since 1900, the Sahara has expanded by 250 km to the south over a stretch of land from west to east 6,000 km long. Lake Chad , located in the Sahel region, has undergone desiccation due to water withdrawal for irrigation and decrease in rainfall. The lake has shrunk by over 90% since 1987, displacing millions of inhabitants. Recent efforts have managed to make some progress toward its restoration, but it
4440-518: The World Economic Forum , 14.5 million more deaths are expected due to climate change by 2050. 30% of the global population currently live in areas where extreme heat and humidity are already associated with excess deaths. By 2100, 50% to 75% of the global population would live in such areas. While total crop yields have been increasing in the past 50 years due to agricultural improvements, climate change has already decreased
4551-414: The carbon cycle . While plants on land and in the ocean absorb most excess emissions of CO 2 every year, that CO 2 is returned to the atmosphere when biological matter is digested, burns, or decays. Land-surface carbon sink processes, such as carbon fixation in the soil and photosynthesis, remove about 29% of annual global CO 2 emissions. The ocean has absorbed 20 to 30% of emitted CO 2 over
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4662-402: The climate system . Solar irradiance has been measured directly by satellites , and indirect measurements are available from the early 1600s onwards. Since 1880, there has been no upward trend in the amount of the Sun's energy reaching the Earth, in contrast to the warming of the lower atmosphere (the troposphere ). The upper atmosphere (the stratosphere ) would also be warming if the Sun
4773-971: The extinction of many species. The oceans have heated more slowly than the land, but plants and animals in the ocean have migrated towards the colder poles faster than species on land. Just as on land, heat waves in the ocean occur more frequently due to climate change, harming a wide range of organisms such as corals, kelp , and seabirds . Ocean acidification makes it harder for marine calcifying organisms such as mussels , barnacles and corals to produce shells and skeletons ; and heatwaves have bleached coral reefs . Harmful algal blooms enhanced by climate change and eutrophication lower oxygen levels, disrupt food webs and cause great loss of marine life. Coastal ecosystems are under particular stress. Almost half of global wetlands have disappeared due to climate change and other human impacts. Plants have come under increased stress from damage by insects. The effects of climate change are impacting humans everywhere in
4884-432: The socioeconomic scenario and the mitigation scenario, models produce atmospheric CO 2 concentrations that range widely between 380 and 1400 ppm. The environmental effects of climate change are broad and far-reaching, affecting oceans , ice, and weather. Changes may occur gradually or rapidly. Evidence for these effects comes from studying climate change in the past, from modelling, and from modern observations. Since
4995-405: The 18th century and 1970 there was little net warming, as the warming impact of greenhouse gas emissions was offset by cooling from sulfur dioxide emissions. Sulfur dioxide causes acid rain , but it also produces sulfate aerosols in the atmosphere, which reflect sunlight and cause global dimming . After 1970, the increasing accumulation of greenhouse gases and controls on sulfur pollution led to
5106-612: The 1950s, droughts and heat waves have appeared simultaneously with increasing frequency. Extremely wet or dry events within the monsoon period have increased in India and East Asia. Monsoonal precipitation over the Northern Hemisphere has increased since 1980. The rainfall rate and intensity of hurricanes and typhoons is likely increasing , and the geographic range likely expanding poleward in response to climate warming. Frequency of tropical cyclones has not increased as
5217-500: The 1980s, the terms global warming and climate change became more common, often being used interchangeably. Scientifically, global warming refers only to increased surface warming, while climate change describes both global warming and its effects on Earth's climate system , such as precipitation changes. Climate change can also be used more broadly to include changes to the climate that have happened throughout Earth's history. Global warming —used as early as 1975 —became
5328-440: The Arctic is forcing many species to relocate or become extinct . Even if efforts to minimize future warming are successful, some effects will continue for centuries. These include ocean heating , ocean acidification and sea level rise . Climate change threatens people with increased flooding , extreme heat, increased food and water scarcity, more disease, and economic loss . Human migration and conflict can also be
5439-435: The Arctic is another major feedback, this reduces the reflectivity of the Earth's surface in the region and accelerates Arctic warming . This additional warming also contributes to permafrost thawing, which releases methane and CO 2 into the atmosphere. Around half of human-caused CO 2 emissions have been absorbed by land plants and by the oceans. This fraction is not static and if future CO 2 emissions decrease,
5550-545: The CO 2 released by the chemical reactions for making cement , steel , aluminum , and fertilizer . Methane emissions come from livestock , manure, rice cultivation , landfills, wastewater, and coal mining , as well as oil and gas extraction . Nitrous oxide emissions largely come from the microbial decomposition of fertilizer . While methane only lasts in the atmosphere for an average of 12 years, CO 2 lasts much longer. The Earth's surface absorbs CO 2 as part of
5661-604: The Earth will be able to absorb up to around 70%. If they increase substantially, it'll still absorb more carbon than now, but the overall fraction will decrease to below 40%. This is because climate change increases droughts and heat waves that eventually inhibit plant growth on land, and soils will release more carbon from dead plants when they are warmer . The rate at which oceans absorb atmospheric carbon will be lowered as they become more acidic and experience changes in thermohaline circulation and phytoplankton distribution. Uncertainty over feedbacks, particularly cloud cover,
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#17327985460015772-488: The Earth. Such variations influence the strength of the West African Monsoon, inducing feedback in vegetation and dust emission that amplify the cycle of wet and dry Sahara climate. There is also a suggestion the transition of the Sahara from savanna to desert during the mid- Holocene was partially due to overgrazing by the cattle of the local population. Research into desertification is complex, and there
5883-643: The Gobi Desert itself is still a distance away from Beijing , reports from field studies state there are large sand dunes forming only 70 km (43.5 mi) outside the city. In Mongolia , around 90% of grassland is considered vulnerable to desertification by the UN. An estimated 13% of desertification in Mongolia is caused by natural factors; the rest is due to human influence particularly overgrazing and increased erosion of soils in cultivated areas. During
5994-591: The International Geosphere-Biosphere Programme (IGBP) and focused specifically on coupled human-environment systems such as land use , and coastal zones . It also had four joint projects on the Earth's carbon cycle , water systems , human health and food systems with the other three global change research programmes (ESSP). IHDP was initiated as the Human Dimensions Programme (HDP) in 1990 by
6105-404: The Mongolia government has listed forest fires , blights , unsustainable forestry and mining activities as leading causes of desertification in the country. The transition from sheep to goat farming in order to meet export demands for cashmere wool has caused degradation of grazing lands. Compared to sheep, goats do more damage to grazing lands by eating roots and flowers. To mitigate
6216-441: The absorption of sunlight, it also increases melting and sea-level rise. Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2 °C by 2050. The effect of decreasing sulfur content of fuel oil for ships since 2020 is estimated to cause an additional 0.05 °C increase in global mean temperature by 2050. As the Sun is the Earth's primary energy source, changes in incoming sunlight directly affect
6327-411: The atmosphere , for instance by increasing forest cover and farming with methods that capture carbon in soil . Before the 1980s it was unclear whether the warming effect of increased greenhouse gases was stronger than the cooling effect of airborne particulates in air pollution . Scientists used the term inadvertent climate modification to refer to human impacts on the climate at this time. In
6438-452: The atmosphere. volcanic CO 2 emissions are more persistent, but they are equivalent to less than 1% of current human-caused CO 2 emissions. Volcanic activity still represents the single largest natural impact (forcing) on temperature in the industrial era. Yet, like the other natural forcings, it has had negligible impacts on global temperature trends since the Industrial Revolution. The climate system's response to an initial forcing
6549-454: The biggest threats to global health in the 21st century. Scientists have warned about the irreversible harms it poses. Extreme weather events affect public health, and food and water security . Temperature extremes lead to increased illness and death. Climate change increases the intensity and frequency of extreme weather events. It can affect transmission of infectious diseases , such as dengue fever and malaria . According to
6660-540: The carbon cycle, such as the fertilizing effect of CO 2 on plant growth. Feedbacks are expected to trend in a positive direction as greenhouse gas emissions continue, raising climate sensitivity. These feedback processes alter the pace of global warming. For instance, warmer air can hold more moisture in the form of water vapour , which is itself a potent greenhouse gas. Warmer air can also make clouds higher and thinner, and therefore more insulating, increasing climate warming. The reduction of snow cover and sea ice in
6771-551: The climate cycled through ice ages . One of the hotter periods was the Last Interglacial , around 125,000 years ago, where temperatures were between 0.5 °C and 1.5 °C warmer than before the start of global warming. This period saw sea levels 5 to 10 metres higher than today. The most recent glacial maximum 20,000 years ago was some 5–7 °C colder. This period has sea levels that were over 125 metres (410 ft) lower than today. Temperatures stabilized in
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#17327985460016882-684: The current interglacial period beginning 11,700 years ago . This period also saw the start of agriculture. Historical patterns of warming and cooling, like the Medieval Warm Period and the Little Ice Age , did not occur at the same time across different regions. Temperatures may have reached as high as those of the late 20th century in a limited set of regions. Climate information for that period comes from climate proxies , such as trees and ice cores . Around 1850 thermometer records began to provide global coverage. Between
6993-403: The degree of warming future emissions will cause when accounting for the strength of climate feedbacks . Models also predict the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere. The physical realism of models is tested by examining their ability to simulate current or past climates. Past models have underestimated
7104-427: The destroyed trees release CO 2 , and are not replaced by new trees, removing that carbon sink . Between 2001 and 2018, 27% of deforestation was from permanent clearing to enable agricultural expansion for crops and livestock. Another 24% has been lost to temporary clearing under the shifting cultivation agricultural systems. 26% was due to logging for wood and derived products, and wildfires have accounted for
7215-681: The development of deserts has occurred naturally over long intervals of time. The modern study of desertification emerged from the study of the 1980s drought in the Sahel . Desertification is a gradual process of increased soil aridity . Desertification has been defined in the text of the United Nations Convention to Combat Desertification (UNCCD) as "land degradation in arid, semi-arid and dry sub-humid regions resulting from various factors, including climatic variations and human activities." Definition of Desert – That area of
7326-669: The difficulty of access to resources and opportunities. Geographic areas most affected are located in Africa ( Sahel region), Asia ( Gobi Desert and Mongolia ) and parts of South America . Drylands occupy approximately 40–41% of Earth's land area and are home to more than 2 billion people. Effects of desertification include sand and dust storms , food insecurity , and poverty . Methods of mitigating or reversing desertification include improving soil quality , greening deserts , managing grazing , and tree-planting ( reforestation and afforestation ). Throughout geological history,
7437-401: The distribution of heat and precipitation around the globe. The World Meteorological Organization estimates there is an 80% chance that global temperatures will exceed 1.5 °C warming for at least one year between 2024 and 2028. The chance of the 5-year average being above 1.5 °C is almost half. The IPCC expects the 20-year average global temperature to exceed +1.5 °C in
7548-444: The dominant direct influence on temperature from land use change. Thus, land use change to date is estimated to have a slight cooling effect. Air pollution, in the form of aerosols, affects the climate on a large scale. Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of sunlight reaching the Earth's surface was observed. This phenomenon is popularly known as global dimming , and
7659-610: The early 2030s. The IPCC Sixth Assessment Report (2021) included projections that by 2100 global warming is very likely to reach 1.0–1.8 °C under a scenario with very low emissions of greenhouse gases , 2.1–3.5 °C under an intermediate emissions scenario , or 3.3–5.7 °C under a very high emissions scenario . The warming will continue past 2100 in the intermediate and high emission scenarios, with future projections of global surface temperatures by year 2300 being similar to millions of years ago. The remaining carbon budget for staying beneath certain temperature increases
7770-470: The earth where the sum of rain and snowfall is much less than other areas, where the annual average rainfall is less than 25CM. Definition by UNO (1995) – Land degradation in barren, humid and sub-humid areas due to climate change and human activities is called desertification. As of 2005, considerable controversy existed over the proper definition of the term desertification with more than 100 formal definitions in existence. The most widely accepted of these
7881-411: The effectiveness of clean energy efforts, and halt most forms of transportation. Dust and sand storms can have a negative effect on the climate which can make desertification worse. Dust particles in the air scatter incoming radiation from the sun (Hassan, 2012). The dust can provide momentary coverage for the ground temperature but the atmospheric temperature will increase. This can disform and shorten
7992-822: The emissions continue to increase for the rest of century, then over 9 million climate-related deaths would occur annually by 2100. Economic damages due to climate change may be severe and there is a chance of disastrous consequences. Severe impacts are expected in South-East Asia and sub-Saharan Africa , where most of the local inhabitants are dependent upon natural and agricultural resources. Heat stress can prevent outdoor labourers from working. If warming reaches 4 °C then labour capacity in those regions could be reduced by 30 to 50%. The World Bank estimates that between 2016 and 2030, climate change could drive over 120 million people into extreme poverty without adaptation. Desertification Desertification
8103-430: The entire atmosphere—is ruled out because only the lower atmosphere has warmed. Atmospheric aerosols produce a smaller, cooling effect. Other drivers, such as changes in albedo , are less impactful. Greenhouse gases are transparent to sunlight , and thus allow it to pass through the atmosphere to heat the Earth's surface. The Earth radiates it as heat , and greenhouse gases absorb a portion of it. This absorption slows
8214-709: The financial impact of desertification in Inner Mongolia , Bai Jingying teaches women how to do traditional embroidery, which they then sell to provide additional income. The Gobi Desert is expanding through desertification, most rapidly on the southern edge into China, which is seeing 3,600 km (1,390 sq mi) of grassland overtaken every year. Dust storms increased in frequency between 1996 and 2016, causing further damage to China's agriculture economy. However, in some areas desertification has been slowed or reversed. The northern and eastern boundaries between desert and grassland are constantly changing. This
8325-1261: The former International Human Dimensions Programme has been carried forward by the Earth System Governance Project . The IHDP Secretariat was located at the United Nations Campus in Bonn, Germany, and was hosted by the United Nations University. IHDP was a partner of the Earth System Science Partnership along with the International Geosphere-Biosphere Programme , the World Climate Research Programme , and DIVERSITAS an international programme for biodiversity research. Climate change Present-day climate change includes both global warming —the ongoing increase in global average temperature —and its wider effects on Earth's climate . Climate change in
8436-604: The global climate system has grown with only brief pauses since at least 1970, and over 90% of this extra energy has been stored in the ocean . The rest has heated the atmosphere , melted ice, and warmed the continents. The Northern Hemisphere and the North Pole have warmed much faster than the South Pole and Southern Hemisphere . The Northern Hemisphere not only has much more land, but also more seasonal snow cover and sea ice . As these surfaces flip from reflecting
8547-490: The gradual and rapid ecosystem changes caused by land use. The study found that, between 1982 and 2015, 6% of the world's drylands underwent desertification driven by unsustainable land use practices compounded by anthropogenic climate change. Despite an average global greening , anthropogenic climate change has degraded 12.6% (5.43 million km ) of drylands, contributing to desertification and affecting 213 million people, 93% of who live in developing economies . There has been
8658-619: The inhabitants of drylands live in developing countries , where they also suffer from poor economic and social conditions. This situation is exacerbated by land degradation because of the reduction in productivity, the precariousness of living conditions and the difficulty of access to resources and opportunities. Many underdeveloped countries are affected by overgrazing, land exhaustion and overdrafting of groundwater due to pressures to exploit marginal drylands for farming. Decision-makers are understandably averse to invest in arid zones with low potential. This absence of investment contributes to
8769-451: The inoculation of tree species with mycorrhiza in arid zones. The mycorrhiza are basically fungi attaching themselves to the roots of the plants. They hereby create a symbiotic relation with the trees, increasing the surface area of the tree's roots greatly (allowing the tree to gather much more nutrient from the soil). The bioengineering of soil microbes, particularly photosynthesizers, has also been suggested and theoretically modeled as
8880-728: The land is classified as drylands and over 68% of the land area has undergone soil erosion as a result of deforestation and overgrazing. 27 to 43% of the land areas in Bolivia, Chile, Ecuador and Peru are at risk due to desertification. In Argentina, Mexico and Paraguay, greater than half the land area is degraded by desertification and cannot be used for agriculture. In Central America, drought has caused increased unemployment and decreased food security - also causing migration of people. Similar impacts have been seen in rural parts of Mexico where about 1,000 km of land have been lost yearly due to desertification. In Argentina , desertification has
8991-666: The land. Agriculture is a main source of income for many desert communities. The increase in desertification in these regions has degraded the land to such an extent where people can no longer productively farm and make a profit. This has negatively impacted the economy and increased poverty rates. There is, however, increased global advocacy e.g. the UN SDG 15 to combat desertification and restore affected lands. Drylands occupy approximately 40–41% of Earth's land area and are home to more than 2 billion people. It has been estimated that some 10–20% of drylands are already degraded,
9102-572: The last 14 million years. Concentrations of methane are far higher than they were over the last 800,000 years. Global human-caused greenhouse gas emissions in 2019 were equivalent to 59 billion tonnes of CO 2 . Of these emissions, 75% was CO 2 , 18% was methane , 4% was nitrous oxide, and 2% was fluorinated gases . CO 2 emissions primarily come from burning fossil fuels to provide energy for transport , manufacturing, heating , and electricity. Additional CO 2 emissions come from deforestation and industrial processes , which include
9213-436: The last two decades. CO 2 is only removed from the atmosphere for the long term when it is stored in the Earth's crust, which is a process that can take millions of years to complete. Around 30% of Earth's land area is largely unusable for humans ( glaciers , deserts , etc.), 26% is forests , 10% is shrubland and 34% is agricultural land . Deforestation is the main land use change contributor to global warming, as
9324-441: The last: internal climate variability processes can make any year 0.2 °C warmer or colder than the average. From 1998 to 2013, negative phases of two such processes, Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) caused a short slower period of warming called the " global warming hiatus ". After the "hiatus", the opposite occurred, with years like 2023 exhibiting temperatures well above even
9435-412: The life time of clouds which can result in less rainfall. Global food security is being threatened by desertification. The more that population grows , the more food that has to be grown. The agricultural business is being displaced from one country to another. For example, Europe on average imports over 50% of its food. Meanwhile, 44% of agricultural land is located in dry lands and it supplies 60% of
9546-608: The lower atmosphere. Carbon dioxide , the primary greenhouse gas driving global warming, has grown by about 50% and is at levels not seen for millions of years. Climate change has an increasingly large impact on the environment . Deserts are expanding , while heat waves and wildfires are becoming more common. Amplified warming in the Arctic has contributed to thawing permafrost , retreat of glaciers and sea ice decline . Higher temperatures are also causing more intense storms , droughts, and other weather extremes . Rapid environmental change in mountains , coral reefs , and
9657-442: The main reason is to maximize yields. By increasing productivity, they require a lot more fertilizer, pesticides, and labor to upkeep machinery. This continuous use of the land rapidly depletes the nutrients of the soil causing desertification to spread. Scientists agree that the existence of a desert in the place where the Sahara desert is now located is due to natural variations in solar insolation due to orbital precession of
9768-661: The marginalization of these zones. When unfavorable agri-climatic conditions are combined with an absence of infrastructure and access to markets, as well as poorly adapted production techniques and an underfed and undereducated population, most such zones are excluded from development. Desertification often causes rural lands to become unable to support the same sized populations that previously lived there. This results in mass migrations out of rural areas and into urban areas particularly in Africa creating unemployment and slums . The number of these environmental refugees grows every year, with projections for sub-Saharan Africa showing
9879-413: The more popular term after NASA climate scientist James Hansen used it in his 1988 testimony in the U.S. Senate . Since the 2000s, climate change has increased usage. Various scientists, politicians and media may use the terms climate crisis or climate emergency to talk about climate change, and may use the term global heating instead of global warming . Over the last few million years
9990-535: The most common causes of desertification was overgrazing, over consumption of vegetation by cattle or other livestock. However, the role of local overexploitation in driving desertification in the recent past is controversial. Drought in the Sahel region is now thought to be principally the result of seasonal variability in rainfall caused by large-scale sea surface temperature variations, largely driven by natural variability and anthropogenic emissions of aerosols (reflective sulphate particles ) and greenhouse gases. As
10101-490: The northern fringe of Africa, southern Africa, and Australia". Drylands cover 41% of the earth's land surface and include 45% of the world's agricultural land. These regions are among the most vulnerable ecosystems to anthropogenic climate and land use change and are under threat of desertification. An observation-based attribution study of desertification was carried out in 2020 which accounted for climate change, climate variability , CO 2 fertilization as well as both
10212-413: The period 1940 to 2015, the mean air temperature increased by 2.24 °C. The warmest ten-year period was during the latest decade to 2021. Precipitation has decreased by 7% over this period resulting in increased arid conditions throughout Mongolia. The Gobi desert continues to expand northward, with over 70% of Mongolia's land degraded through overgrazing, deforestation, and climate change. In addition,
10323-586: The physical expansion of deserts has been rejected as the concept has further evolved since then. There exists also controversy around the sub-grouping of types of desertification, including, for example, the validity and usefulness of such terms as "man-made desert" and "non-pattern desert". The immediate cause of desertification is the loss of most vegetation. This is driven by a number of factors, alone or in combination, such as drought, climatic shifts, tillage for agriculture, overgrazing and deforestation for fuel or construction materials. Though vegetation plays
10434-511: The potential to disrupt the nation's food supply. Techniques and countermeasures exist for mitigating or reversing desertification. For some of these measures, there are numerous barriers to their implementation. Yet for others, the solution simply requires the exercise of human reason. One proposed barrier is that the costs of adopting sustainable agricultural practices sometimes exceed the benefits for individual farmers, even while they are socially and environmentally beneficial. Another issue
10545-579: The project by planting 50,000 acres of trees. It is said to have improved land quality and caused an increase in economic opportunity in the region. Another major area that is being impacted by desertification is the Gobi Desert located in Northern China and Southern Mongolia. The Gobi Desert is the fastest expanding desert on Earth, as it transforms over 3,600 square kilometres (1,400 square miles) of grassland into wasteland annually. Although
10656-619: The rate at which heat escapes into space, trapping heat near the Earth's surface and warming it over time. While water vapour (≈50%) and clouds (≈25%) are the biggest contributors to the greenhouse effect, they primarily change as a function of temperature and are therefore mostly considered to be feedbacks that change climate sensitivity . On the other hand, concentrations of gases such as CO 2 (≈20%), tropospheric ozone , CFCs and nitrous oxide are added or removed independently from temperature, and are therefore considered to be external forcings that change global temperatures. Before
10767-522: The rate of Arctic shrinkage and underestimated the rate of precipitation increase. Sea level rise since 1990 was underestimated in older models, but more recent models agree well with observations. The 2017 United States-published National Climate Assessment notes that "climate models may still be underestimating or missing relevant feedback processes". Additionally, climate models may be unable to adequately predict short-term regional climatic shifts. A subset of climate models add societal factors to
10878-622: The rate of yield growth . Fisheries have been negatively affected in multiple regions. While agricultural productivity has been positively affected in some high latitude areas, mid- and low-latitude areas have been negatively affected. According to the World Economic Forum, an increase in drought in certain regions could cause 3.2 million deaths from malnutrition by 2050 and stunting in children. With 2 °C warming, global livestock headcounts could decline by 7–10% by 2050, as less animal feed will be available. If
10989-405: The recent average. This is why the temperature change is defined in terms of a 20-year average, which reduces the noise of hot and cold years and decadal climate patterns, and detects the long-term signal. A wide range of other observations reinforce the evidence of warming. The upper atmosphere is cooling, because greenhouse gases are trapping heat near the Earth's surface, and so less heat
11100-411: The release of chemical compounds that influence clouds, and by changing wind patterns. In tropic and temperate areas the net effect is to produce significant warming, and forest restoration can make local temperatures cooler. At latitudes closer to the poles, there is a cooling effect as forest is replaced by snow-covered (and more reflective) plains. Globally, these increases in surface albedo have been
11211-476: The remaining 23%. Some forests have not been fully cleared, but were already degraded by these impacts. Restoring these forests also recovers their potential as a carbon sink. Local vegetation cover impacts how much of the sunlight gets reflected back into space ( albedo ), and how much heat is lost by evaporation . For instance, the change from a dark forest to grassland makes the surface lighter, causing it to reflect more sunlight. Deforestation can also modify
11322-446: The rule in the Sahel region. The Sahel has lost approximately 650,000 km of its productive agricultural land over the past 50 years; the propagation of desertification in this area is considerable. The climate of the Sahara has undergone enormous variations over the last few hundred thousand years, oscillating between wet (grassland) and dry (desert) every 20,000 years (a phenomenon believed to be caused by long-term changes in
11433-585: The scientific field provided leadership in the selection and development of themes for focused research and in stimulating scientific communities to coordinate their efforts on these themes within the framework of its projects. IHDP research was conducted through ten projects. Its six core projects, focused on how humans affect and are affected by climate change , with specific topics including human security , urbanization , industrial transformation and environmental governance as they relate to global change . Two of its six core projects were also core projects of
11544-583: The sea levels by at least 3.3 m (10 ft 10 in) over approximately 2000 years. Recent warming has driven many terrestrial and freshwater species poleward and towards higher altitudes . For instance, the range of hundreds of North American birds has shifted northward at an average rate of 1.5 km/year over the past 55 years. Higher atmospheric CO 2 levels and an extended growing season have resulted in global greening. However, heatwaves and drought have reduced ecosystem productivity in some regions. The future balance of these opposing effects
11655-402: The soil and restoration of its fertility is often achieved by plants. Of these, leguminous plants which extract nitrogen from the air and fix it in the soil, succulents (such as Opuntia ), and food crops/trees as grains , barley , beans and dates are the most important. Sand fences can also be used to control drifting of soil and sand erosion. Another way to restore soil fertility
11766-444: The soil is often done through the use of shelter belts , woodlots and windbreaks . Windbreaks are made from trees and bushes and are used to reduce soil erosion and evapotranspiration . Some soils (for example, clay ), due to lack of water can become consolidated rather than porous (as in the case of sandy soils). Some techniques as zaï or tillage are then used to still allow the planting of crops. Another technique that
11877-492: The total area affected by desertification being between 6 and 12 million square kilometers, that about 1–6% of the inhabitants of drylands live in desertified areas, and that a billion people are under threat from further desertification. The impact of climate change and human activities on desertification are exemplified in the Sahel region of Africa. The region is characterized by a dry hot climate, high temperatures and low rainfall (100–600 mm per year). So, droughts are
11988-477: The world's food production. Desertification is decreasing the amount of sustainable land for agricultural uses but demands are continuously growing. In the near future, the demands will overcome the supply. The violent herder–farmer conflicts in Nigeria , Sudan , Mali and other countries in the Sahel region have been exacerbated by climate change , land degradation and population growth . At least 90% of
12099-438: The world. Impacts can be observed on all continents and ocean regions, with low-latitude, less developed areas facing the greatest risk. Continued warming has potentially "severe, pervasive and irreversible impacts" for people and ecosystems. The risks are unevenly distributed, but are generally greater for disadvantaged people in developing and developed countries. The World Health Organization calls climate change one of
12210-524: Was sending more energy to Earth, but instead, it has been cooling. This is consistent with greenhouse gases preventing heat from leaving the Earth's atmosphere. Explosive volcanic eruptions can release gases, dust and ash that partially block sunlight and reduce temperatures, or they can send water vapour into the atmosphere, which adds to greenhouse gases and increases temperatures. These impacts on temperature only last for several years, because both water vapour and volcanic material have low persistence in
12321-618: Was that of the Princeton University Dictionary which defined it as "the process of fertile land transforming into desert typically as a result of deforestation , drought or improper/inappropriate agriculture". This definition clearly demonstrated the interconnectedness of desertification and human activities, in particular land use and land management practices. It also highlighted the economic, social and environmental implications of desertification. However, this original understanding that desertification involved
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