Regional effects of global warming

Regional effects of global warming are long-term significant changes in the expected patterns of average weather of a specific region due to global warming. The world average temperature is rising due to the greenhouse effect caused by increasing levels of greenhouse gases, especially carbon dioxide. When the global temperature changes, the changes in climate are not expected to be uniform across the Earth. In particular, land areas change more quickly than oceans, and northern high latitudes change more quickly than the tropics, and the margins of biome regions change faster than do their cores.

Regional effects of global warming vary in nature. Some are the result of a generalised global change, such as rising temperature, resulting in local effects, such as melting ice. In other cases, a change may be related to a change in a particular ocean current or weather system. In such cases, the regional effect may be disproportionate and will not necessarily follow the global trend.

There are three major ways in which global warming will make changes to regional climate: melting or forming ice, changing the hydrological cycle (of evaporation and precipitation) and changing currents in the oceans and air flows in the atmosphere. The coast can also be considered a region, and will suffer severe impacts from sea level rise.

Especially affected regions

The Arctic, Africa, small islands and Asian megadeltas are regions that are likely to be especially affected by future climate change.^[1] Within other areas, some people are particularly at risk from future climate change, such as the poor, young children and the elderly.^[1]

The Arctic is likely to be especially affected by climate change because of the high projected rate of regional warming and associated impacts.^[1] Temperature projections for the Arctic region were assessed by Anisimov et al. (2007).^[2] These suggested areally averaged warming of about 2 °C to 9 °C by the year 2100. The range reflects different projections made by different climate models, run with different forcing scenarios. Radiative forcing is a measure of the effect of natural and human activities on the climate. Different forcing scenarios reflect, for example, different projections of future human greenhouse gas emissions.

Africa is likely to be the continent most vulnerable to climate change.^[3] With high confidence, Boko et al. (2007) projected that in many African countries and regions, agricultural production and food security would likely be severely compromised by climate change and climate variability.^[4]

On small islands, sea level rise is expected to exacerbate inundation, erosion and other coastal hazards, and threaten vital infrastructure, human settlements and facilities that support the livelihood of island communities.^[5] In the coastal zone of Asia, there are 11 megadeltas with an area greater than 10,000 km².^[6] These megadeltas are homes to millions of people, and contain diverse ecosystems. Climate change and sea level rise could increase the frequency and level of inundation of Asian megadeltas due to storm surges and floods from river drainage.

Ice-cover changes

Permanent ice cover on land is a result of a combination of low peak temperatures and sufficient precipitation. Some of the coldest places on Earth, such as the dry valleys of Antarctica, lack significant ice or snow coverage due to a lack of snow. Sea ice however maybe formed simply by low temperature, although precipitation may influence its stability by changing albedo, providing an insulating covering of snow and affecting heat transfer. Global warming has the capacity to alter both precipitation and temperature, resulting in significant changes to ice cover. Furthermore, the behaviour of ice sheets, ice caps and glaciers is altered by changes in temperature and precipitation, particularly as regards the behaviour of water flowing into and through the ice.

Arctic sea ice

Arctic sea ice minima in 2005, 2007, and the 1979-2000 average.

Recent projections of sea ice loss suggest that the Arctic ocean will likely be free of summer sea ice sometime between 2059 and 2078.^[7]

Models showing decreasing sea ice also show a corresponding decrease in polar bear habitat.^[8] Some scientists see the polar bear as a species which will be affected first and most severely by global warming because it is a top-level predator in the Arctic,^[9] which is projected to warm more than the global average.^[10] Recent reports show polar bears resorting to cannibalism,^[11] and scientists state that these are the only instances that they have observed of polar bears stalking and killing one another for food.^[12]

Antarctica

The collapse of Larsen B, showing the diminishing extent of the shelf from 1998 to 2002

The Antarctic peninsula has lost a number of ice shelves recently. These are large areas of floating ice which are fed by glaciers. Many are the size of a small country. The sudden collapse of the Larsen B ice shelf in 2002^[13] took 5 weeks or less and may have been due to global warming.^[14] Larsen B had previously been stable for up to 12,000 years.^[15]

Concern has been expressed about the stability of the West Antarctic ice sheet. A collapse of the West Antarctic ice sheet could occur "within 300 years [as] a worst-case scenario. Rapid sea-level rise (>1 m per century) is more likely to come from the WAIS than from the [Greenland ice sheet]."^[16]

Greenland

As the Greenland ice sheet loses mass from calving of icebergs as well as by melting of ice, any such processes tend to accelerate the loss of the ice sheet.^[17]

The IPCC suggest that Greenland will become ice free at around 5C over pre-industrial levels,^{[citation needed]} but subsequent research comparing data from the Eemian period suggests that the ice sheet will remain at least in part at these temperatures.^[18] The volume of ice in the Greenland sheet is sufficient to cause a global sea level rise of 7 meters. It would take 3,000 years to completely melt the Greenland ice sheet.^[19] This figure was derived from the assumed levels of greenhouse gases over the duration of the experiment. In reality, these greenhouse gas levels are of course affected by future emissions and may differ from the assumptions made in the model.

Glaciers

Glacier retreat not only affects the communities and ecosystems around the actual glacier, but the entire downstream region. The most notable example of this is in India, where river systems such as the Indus and Ganges are ultimately fed by glacial meltwater from the Himalayas. Loss of these glaciers will have dramatic effects on the downstream region, increasing the risk of drought as lower flows of meltwater reduce summer river flows unless summer precipitation increases. Altered patterns of flooding can also affect soil fertility.^[20]

The Tibetan Plateau contains the world's third-largest store of ice. Qin Dahe, the former head of the China Meteorological Administration, said that the recent fast pace of melting and warmer temperatures will be good for agriculture and tourism in the short term; but issued a strong warning:

"Temperatures are rising four times faster than elsewhere in China, and the Tibetan glaciers are retreating at a higher speed than in any other part of the world.... In the short term, this will cause lakes to expand and bring floods and mudflows. . . . In the long run, the glaciers are vital lifelines for Asian rivers, including the Indus and the Ganges. Once they vanish, water supplies in those regions will be in peril."^[21]

Permafrost regions

Regions of permafrost cover much of the Arctic. In many areas, permafrost is melting, leading to the formation of a boggy, undulating landscape filled with thermokarst lakes and distinctive patterns of drunken trees. The process of permafrost melting is complex and poorly understood since existing models do not include feedback effects such as the heat generated by decomposition.^{[22][citation needed]}

Arctic permafrost soils are estimated to store twice as much carbon as is currently present in the atmosphere in the form of CO2. Warming in the Arctic is causing increased emissions of CO2 and Methane (CH₄).^[23]

Precipitation and vegetation changes

The Eastern Amazon rainforest may be replaced by Caatinga vegetation as a result of global warming.

Much of the effect of global warming is felt through its influence on rain and snow. Regions may become wetter, drier, or may experience changes in the intensity of precipitation - such as moving from a damp climate to one defined by a mixture of floods and droughts. These changes may have a very severe impact on both the natural world and human civilisation, as both naturally occurring and farmed plants experience regional climate change that is beyond their ability to tolerate.

A U.S. National Oceanic and Atmospheric Administration (NOAA) analysis published in the Journal of Climate October 2011, and cited on Joseph J. Romm's, climateprogress.org, found that increasing droughts in the Middle East during the wintertime when the region traditionally most of its rainfall to replenish aquifers, and anthropogenic climate change is partly responsible. Per Earth System Research Laboratory's Martin Hoerling “The magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone,” and “This is not encouraging news for a region that already experiences water stress, because it implies natural variability alone is unlikely to return the region’s climate to normal.” the lead author of the paper.^[24] Twelve of the world’s fifteen most water-scarce countries — Bahrain, Qatar, Algeria, Libya, Tunisia, Jordan, Saudi Arabia, Yemen, Oman, the United Arab Emirates, Kuwait, Israel and Palestine — are in the Middle East.

Amazon

One modeling study suggested that the extent of the Amazon rainforest may be reduced by 70% if global warming continues unchecked, due to regional precipitation changes that result from weakening of large-scale tropical circulation.^[25]

Sahara

Some studies suggest that the Sahara desert have been more vegetated during the warmer Mid-Holocene period, and that future warming may result in similar patterns.^{[26][27][clarification needed]}

Sahel

Climate models which realistically^{[clarification needed]} model the West African Monsoon predict "a doubling of the number of anomalously dry years [in the Sahel] by the end of the century".^{[16][clarification needed]}

Desert expansion

Expansion of subtropical deserts is expected as a result of global warming, due to expansion of the Hadley Cell.^[28]

Coastal regions

Past sea-level changes and relative temperatures. Global warming is expected to dramatically affect sea level.

Global sea level is currently rising due to the thermal expansion of water in the oceans^[29] and the addition of water from ice sheets.^[30] Because of this, there low-lying coastal areas, many of which are heavily populated, are at risk of flooding.^[31][32]

Areas threatened by current sea level rise include Tuvalu^[33] and the Maldives.^{[34][unreliable source?]} Regions that are prone to storm surges, such as London, are also threatened.^[35]

With very high confidence, IPCC (2007) projected that by the 2080s, many millions more people would experience floods every year due to sea level rise.^[36] The numbers affected were projected to be largest in the densely populated and low-lying megadeltas of Asia and Africa. Small islands were judged to be especially vulnerable.

Ocean effects

North Atlantic region

It has been suggested that a shutdown of the Atlantic thermohaline circulation may result in relative cooling of the North Atlantic region by up to 8C in certain locations.^[37] Recent research suggests that this process is not currently underway.^[38]

Tropical surface and troposphere temperatures

In the tropics, basic physical considerations, climate models, and multiple independent data sets indicate that the warming trend due to well-mixed greenhouse gases should be faster in the troposphere than at the surface.^[39]

See also

Global warming portal

• Arctic methane release
• Climate change in the Arctic
• Intertropical Convergence Zone (ITCZ)
• Sea level rise
• Shutdown of thermohaline circulation
• Effects of global warming

References

External links

• Impacts of global warming by country from the Met Office Hadley Centre
• Video on the effects of global warming in the polar region Bering Sea