cause vegetation to dry out. when a fire starts in an area with very dry vegetation, it can spread rapidly. higher temperatures can also lengthen the fire season, the time of year in which severe wildfires are most likely, particularly in regions where snow is disappearing. even though weather conditions are raising the risks of wildfires, the total area burnt by wildfires has decreased. this is mostly because savanna has been converted to cropland, so there are fewer trees to burn. prescribed burning, an indigenous practice in the us and australia, can reduce wildfire burning. the carbon released from wildfires can further increase greenhouse gas concentrations. this feedback is not yet fully integrated into climate models.: 20 oceans oceans have taken up almost 90% of the excess heat accumulated on earth due to global warming. part of the great barrier reef in australia in 2016 after a coral bleaching event this section is an excerpt from effects of climate change on oceans. among the effects of climate change on oceans are an increase of ocean temperatures, more frequent marine heatwaves, ocean acidification, a rise in sea levels, sea ice decline, increased ocean stratification, reductions in oxygen levels, changes to ocean currents including a weakening of the atlantic meridional overturning circulation. all these changes have knock-on effects which disturb marine ecosystems. the primary factor causing these changes is climate change due to human-caused emissions of greenhouse gases, such as carbon dioxide and methane. this leads inevitably to ocean warming, because the ocean is taking up most of the additional heat in the climate system. the ocean absorbs some of the extra carbon dioxide in the atmosphere and this causes the ph value of the ocean to drop. it is estimated that the ocean absorbs about 25% of all human-caused co2 emissions. ocean temperature stratification increases as the ocean surface warms due to rising air temperatures.: 471 the decline in mixing of the ocean layers stabilises warm water near the surface while reducing cold, deep water circulation. the reduced up and down mixing reduces the ability of the ocean to absorb heat, directing a larger fraction of future warming toward the atmosphere and land. the amount of energy available for tropical cyclones and other storms is expected to increase, while nutrients for fish in the upper ocean layers are expected to decrease, as is the ocean's capacity to store carbon. at the same time, contrasts in salinity are increasing: salty areas are becoming saltier and fresher areas less salty. warmer water cannot contain the same amount of oxygen as cold water. as a result, oxygen from the oceans moves to the atmosphere. increased thermal stratification may result in a reduced supply of oxygen from surface waters to deeper waters, lowering the water's oxygen content further. the ocean has already lost oxygen throughout its water column, and oxygen minimum zones are expanding worldwide.: 471 sea level rise this section is an excerpt from sea level rise. global sea level rise from 1880 between 1901 and 2018, the average global sea level rose by 15–25 cm (6–10 in), or 1–2 mm per year. this rate is increasing; sea levels are now rising at a rate of 3.7 mm (0.146 inches) per year. human-caused climate change is predominantly the cause, as it constantly heats (and thus expands) the ocean and melts land-based ice sheets and glaciers. between 1993 and 2018, thermal expansion of water contributed 42% to sea level rise (slr); melting of temperate glaciers contributed 21%; greenland contributed 15%; and antarctica contributed 8%.: 1576 because sea level rise lags changes in earth temperature, it will continue to accelerate between now and 2050 purely in response to already-occurring warming; whether it continues to accelerate after that depends on human greenhouse gas emissions. if global warming is limited to 1.5 °c (2.7 °f), then sea level rise does not accelerate, but it would still amount to 2–3 m (7–10 ft) over the next 2000 years, while 19–22 metres (62–72 ft) would occur if the warming peaks at 5 °c (9.0 °f).: 21 rising seas pose both a direct risk of flooding unprotected areas and indirect threats of higher storm surges, king tides, and tsunamis. they also drive impacts such as loss of coastal ecosystems like mangroves, losses in crop production due to salinization of irrigation water, and the disruption of sea trade due to damaged ports. just the projected sea level rise by 2050 will expose places currently inhabited by tens of millions of people to annual flooding. this may increase to hundreds of millions in the latter decades of the century if greenhouse gas emissions are not reduced drastically. while slow increases in sea level may allow time for adaptation, such as building sea walls, the passage of time can also increase the number of people at risk, as many coastal areas have large population growth. later in the century, millions more would be affected in cities such as miami, rio de janeiro, osaka and shanghai under the warming of 3 °c (5.4 °f), which is close to the current trajectory. ice and snow earth lost 28 trillion tonnes of ice between 1994 and 2017, with melting grounded ice (ice sheets and glaciers) raising the global sea level by 34.6 ±3.1 mm. the rate of ice loss has risen by 57% since the 1990s−from 0.8 to 1.2 trillion tonnes per year. melting of glacial mass is approximately linearly related to temperature rise. shrinkage of snow cover duration in the alps, starting ca. end of the 19th century, highlighting climate change adaptation needs. the cryosphere, the area of the earth covered by snow or ice, is extremely sensitive to changes in global climate. there has been an extensive loss of snow on land since 1981. some of the largest declines have been observed in the spring. during the 21st century, snow cover is projected to continue its retreat in almost all regions. glaciers and ice sheets decline since the beginning of the twentieth century, there has been a widespread retreat of glaciers.: 1215 those glaciers that are not associated with the polar ice sheets lost around 8% of their mass between 1971 and 2019.: 1275 in the andes in south america and in the himalayas in asia, the retreat of glaciers could impact water supply. the melting of those glaciers could also cause landslides or glacial lake outburst floods. the melting of the greenland and west antarctic ice sheets will continue to contribute to sea level rise over long time-scales. the greenland ice sheet loss is mainly driven by melt from the top, whereas antarctic ice loss is driven by warm ocean water melting the outlet glaciers.: 1215 future melt of the west antarctic ice sheet is potentially abrupt under a high emission scenario, as a consequence of a partial collapse. part of the ice sheet is grounded on bedrock below sea level, making it possibly vulnerable to the self-enhancing process of marine ice sheet instability. a further hypothesis is that marine ice cliff instability would also contribute to a partial collapse, but limited evidence is available for its importance.: 1269–1270 a partial collapse of the ice sheet would lead to rapid sea level rise and a local decrease in ocean salinity. it would be irreversible on a timescale between decades and millennia. the complete loss of the west antarctic ice sheet would cause over 5 metres (16 ft) of sea level rise. in contrast to the west antarctic ice sheet, melt of the greenland ice sheet is projected to be taking place more gradually over millennia. sustained warming between 1 °c (1.8 °f) (low confidence) and 4 °c (7.2 °f) (medium confidence) would lead to a complete loss of the ice sheet, contributing 7 m (23 ft) to sea levels globally. the ice loss could become irreversible due to a further self-enhancing feedback: the elevation-surface mass balance feedback. when ice melts on top of the ice sheet, the elevation drops. as air temperature is higher at lower altitude, this promotes further melt. sea ice decline sea ice reflects 50% to 70% of the incoming solar radiation back into space, while only 6% of the incoming solar energy is reflected by the ocean. as the climate warms, the area covered by snow or sea ice decreases. after sea ice melts, more energy is absorbed by the ocean, thus warming it. this ice-albedo feedback is a self-reinforcing feedback of climate change. large-scale measurements of sea ice have only been possible since the satellite era. sea ice in the arctic has declined in recent decades in area and volume due to climate change. it has been melting more in summer than it refreezes in winter. the decline of sea ice in the arctic has been accelerating during the early twenty‐first century, with a decline rate of 4.7% per decade (it has declined over 50% since the first satellite records). while ice-free summers are expected to be rare at 1.5 °c (2.7 °f) degrees of warming, they are set to occur at least once every decade at a warming level of 2 °c (3.6 °f). the arctic will likely become ice-free at the end of some summers before 2050.: 9 sea ice extent in antarctica varies a lot year by year. this makes it difficult to determine a trend, and record highs and record lows have been observed between 2013 and 2023. the general trend since 1979, the start of the satellite measurements, has been roughly flat. between 2015 and 2023, there has been a decline in sea ice, but due to the high variability, this does not correspond to a significant trend. permafrost thawing globally, permafrost warmed by about 0.3 °c between 2007 and 2016. permafrost extent has been diminishing for decades, and more decline is expected in the future.: 1280 permafrost thaw makes the ground weaker and unstable. in areas with much permafrost, nearby human infrastructure such as railways, settlements and pipelines may be damaged severely by the thaw.: 236 furthermore, thawing soil can release methane and co2 from microbial decomposition. this can generate a strong feedback loop to global warming. it is believed that carbon storage in permafrost globally is approximately 1600 gigatons, twice the atmospheric pool. wildlife and nature main article: effects of climate change on ecosystems recent warming has strongly affected natural biological systems. species worldwide are moving poleward to colder areas. on land, species may move to higher elevations, whereas marine species find colder water at greater depths. of the drivers with the biggest global impact on nature, climate change ranks third over the five decades before 2020, with only change in land use and sea use, and direct exploitation of organisms having a greater impact. the impacts of climate change in nature are projected to become more pronounced in the next few decades. the stresses caused by climate change, added to other stresses on ecological systems (e.g. land conversion, land degradation, harvesting, and pollution), threaten substantial damage to or complete loss of some unique ecosystems, and extinction of species. key interactions between species within ecosystems are often disrupted because species from one location do not leave the warming habitat at the same rate, giving rise to rapid changes in the functioning of the ecosystem. impacts include changes in regional rainfall patterns, earlier leafing of trees and plants over many regions; movements of species to higher latitudes and altitudes; changes in bird migrations; and shifting of the oceans' plankton and fish from cold- to warm-adapted communities. these changes of land and ocean ecosystems have direct effects on human well-being. for instance, ocean ecosystems help with coastal protection and provide food. freshwater and land ecosystems can deliver freshwater for human consumption. furthermore, these ecosystems can store carbon, which acts as a stabilising feedback to climate change. ecosystems on land climate change has been estimated to be a major driver of biodiversity loss in cool conifer forests, savannas, mediterranean-climate systems, tropical forests, and the arctic tundra. in other ecosystems, land-use change may be a stronger driver of biodiversity loss, at least in the near-term. beyond the year 2050, climate change may be the major driver for biodiversity loss globally. climate change interacts with other pressures such as habitat modification, pollution and invasive species. interacting with these pressures, climate change increases extinction risk for