Climate Change

Submitted by Arthur Dahl on 5. June 2011 - 18:09
e-learning centre on sustainable development


Heading: Environment    Topic: Climate Change

The latest scientific evidence suggests that climate change may be close to a tipping point, and the worst case scenarios of rapid climate change with positive feedbacks may represent what is actually happening. Global warming is expected to be most severe at the poles, and recent reports show that this is now taking place:
- the Arctic Ocean lost 14% of its permanent ice in 2005, a further 23% in 2007, and nearly as much in 2008, when the Northwest Passage became navigable for the first time;
- the permafrost in Siberia and Canada is melting so rapidly that half may be gone by 2050 and 90% by 2100, releasing hundreds of billions of tonnes of methane, a potent greenhouse gas (Pearce 2006);
- the rate at which the sea level is rising doubled to 2mm per year over the last 150 years and has now doubled again to 4 mm due to increasing loss of Antarctic ice (Velicogna et al. 2006), threatening to create at least 8 million refugees from lowlying deltas alone (Hecht 2006); and
- the rate of flow of the largest Greenland glaciers into the sea has doubled in the last few years to 14 kilometres per year (Luckman et al. 2006) and the annual volume of ice lost has more than doubled in a decade to 220 cubic kilometres because of a 3°C rise in temperature (Rignot et al. 2006), leading to predictions of a collapse in the Greenland ice cap with a rise in sea level of two metres this century and several more next century (Hansen 2006).

A report that the Gulf Stream had recently slowed by 30% (Bryden et al. 2005), possibly as a result of increasing freshwater flow into the Arctic Ocean from melting ice (Pearce 2006), has not been confirmed as further data are inconclusive. A continued decline could reduce winter temperatures in northwest Europe by 4-6°C (Bryden et al. 2005).

The scientific assessment

The Intergovernmental Panel on Climate Change (IPCC) fourth scientific assessment (IPCC 2007) states that warming of the climate system is unequivocal, as observed in rising air and ocean temperatures, widespread melting of snow and ice and rising sea levels. The land is warming faster than the oceans, especially in the northern polar region. The IPCC shared the 2007 Nobel Peace Prize with Al Gore for alerting the world to the threats to human security from climate change.

Emissions from human activities of the main greenhouse gases (GHG), carbon dioxide (CO2), methane and nitrous oxide have grown since pre-industrial times, and increased 70% between 1970 and 2004, and this observed increase in anthropogenic greenhouse gas concentrations in the atmosphere is very likely to have caused the observed increase in global average temperature, when natural factors should have caused a cooling. This discernable human influence now extends to sea level rise, changes in wind patterns and storm tracks, extreme hot and cold nights, heat waves, spreading drought and more frequent heavy precipitation. Under current mitigation policies, GHG emissions will continue to grow, causing further warming and larger changes than those observed so far (IPCC 2007).

An increasing body of observation gives a collective picture of a warming world. Eleven of the last 12 years rank among the 12 warmest years since measurements started in 1850. Many natural systems are being affected by regional climate changes, particularly temperature increases. Rising CO2 levels are also causing ocean acidification, affecting corals and other shell-producing animals (IPCC 2007). Data from tree rings, corals, ice cores and historical records for the Northern Hemisphere indicate that the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1000 years (IPCC 2001). Anthropogenic warming and sea level rise will continue for centuries, even if GHG levels are stabilized, and there may be abrupt and possibly irreversable impacts (IPCC 2007).

In the mid- and high-latitudes of the northern hemisphere, snow cover has decreased by about 10% since the late 1960s, and the annual duration of lake- and river-ice cover has shortened by about two weeks over the 20th century. There has been about a 40% decline in Arctic sea-ice thickness during late summer to early autumn in recent decades (IPCC 2001), and melting of permanent ice is accelerating.

Since 1750, the atmospheric concentration of carbon dioxide has increased from 280 parts per million to over 390 ppm, and the rise has accelerated since 2000. The present CO2 concentration has not been exceeded during the past 420,000 years and likely not during the past 20 million years.

Global average water vapour concentration and precipitation are projected to increase. More intense precipitation events are likely over many northern hemisphere’s mid- to high-latitude land areas. While the observed frequencies of tropical and extra-tropical cyclones and severe local storms currently show no clear long-term trends, there has been a significant increase in the most extreme storms since the 1970s in all oceans.

The string of record warm years and other signs of climate disruption continues the trend already documented in the previous IPCC reports and other studies (IPCC 2007; IPCC, 1995; Pearce, 1995c; Karl, 1998). The greatest temperature increase has been in the southern hemisphere (Salinger, et al. 1994; Bindoff and Church, 1992), and ice shelves are retreating significantly on the Antarctic Peninsula (Johannessen, et al., 1995; Vaughan and Doake, 1996). However, the effects of change are already and will probably continue to be seen in the northern hemisphere as well: according to a report published by the Department of the Environment in the UK, London will be as hot as the Loire Valley within 20 years (Parry et al., 1996). Sulphate aerosols have counteracted warming in industrialized areas of the northern hemisphere, at least on a short-term basis (IPCC, 1995; Pearce, 1995b), but as air pollution is controlled, this effect should diminish.

New evidence also shows that climate can change or oscillate more rapidly than expected, and that deep ocean currents may be part of the control mechanism. Worse yet, a process of ice formation off Greenland which drives one of these deep currents and helps to maintain the Gulf Stream (responsible for the mild western European climate), failed completely in 1994, probably as a result of global warming (Grootes et al., 1993; IPCC, 1995; Wadhams, 1996). The deep waters of the Atlantic, Pacific and Indian Oceans have also warmed in the last few decades (Salinger et al. 1994; Bindoff and Church, 1992; Parrilla et al., 1994). The role of oceans in absorbing carbon dioxide and stabilizing climate may also be affected by changes in plankton populations (Lovelock and Kump, 1994); ocean surface warming off California is associated with a decrease in zooplankton of 80 percent since 1951 (Roemmich and McGowan, 1995), and a significant change in intertidal marine life (Barry et al., 1995), with warm-water species moving up the coast and colder-water species retreating. It is these lateral shifts in temperature patterns that may be the most important signal of global warming. The sea surface has also warmed significantly in the western Pacific off Japan (Japanese Maritime Safety Agency, 1995).

New studies show that methane emissions from natural wetlands have serious implications for global warming. Methane, a much more potent greenhouse gas than CO2, is produced in summer from wetlands in western Siberia, leading to high atmospheric concentrations. In eastern Siberia, methane is produced in the sediments of permafrost lakes, and large quantities of methane are stored in permafrost. Warming in permafrost areas of Siberia and Canada would increase methane emissions to the atmosphere significantly (Dallimore and Collett, 1995), and this now seems to be happening (Pearce 2006). While forests were thought to be beneficial in absorbing carbon dioxide, they have recently been found to be important producers of methane as well.

Climate inertia and the long life of gases mean that the full effects of past emissions will occur even if future emissions are reduced, slowing the effect of emissions reductions. Even if industrialized countries reduce emissions by 30-90 percent, global emissions would reach two to three times 1990 levels, so a slow start is difficult to correct later. There are large margins of error in calculating natural sources and sinks, such that an accurate calculation for terrestrial sources and sinks is not presently possible (ENB, 1997).

The IPCC has assessed regional vulnerability to climate change impacts in 10 regions, because the ability to predict impacts for specific places and times is limited. It concluded that ecosystems, especially forests and coral reefs, are highly sensitive to climate change. Billions of people could be affected by exacerbated problems in drinking water supply, sanitation, and drought. Food production could decrease in the tropics and subtropics, despite steady global production. Significant adverse effects on small island States and low-lying deltas such as in Bangladesh, Egypt and China could displace tens of millions of people with one meter of sea-level rise. Heat stress mortality and vector-borne diseases could increase. Most effects are negative for the most vulnerable developing countries (ENB, 1997).

Much of the controversy about proving the reality of climate change is because the wrong effects are being measured. The effects should appear not as global warming, since the tropics will show little temperature change, but as global heating expressed by increased variability and shifts in the latitude of biological and climatological features in temperate regions.  The tropics will grow wider and the polar regions will shrink. These effects are already being demonstrated (Barry et al. 1995). An increased frequency of the El Niño/Southern Oscillation and other ocean/atmosphere oscillations, and more severe storms, could be a result of increased energy available from global heating. The biggest recent concern, based on coupled ocean/atmosphere models, is of major changes in the oceans, particularly the Southern Ocean, such as more stability in ocean temperature gradients and a reduction of nearly a quarter in ocean fertility over the next 75 years. This would reduce the capacity of the oceans to take up carbon dioxide, thus further accelerating the greenhouse effect (AtKisson, 1997).

One positive result of the focus on climate change has been significant progress in methods of climate prediction and impact assessment, particularly with reference to inter-annual changes such as variations in rainfall associated with the El Niño-Southern Oscillation. This is now possible because of increased ocean observations from automatic buoys and satellites, new means of network communications, and the capability to monitor climate anomalies in near-real-time on a global basis. See for example the satellite data on the El Niño phenomenon at the Jet Propulsion Laboratory If adequately supported and made operational through the Global Climate Observing System, mechanisms to make such predictions could provide significant economic benefits in many regions (Cane et al., 1994; WMO, 1995).

Action to control greenhouse gases causing climate change

The nations of the world adopted the UN Framework Convention on Climate Change at the Earth Summit in Rio de Janeiro in 1992. They then agreed in the Kyoto Protocol on the reduction of greenhouse gases to return emissions to 1990 levels by 2012. However, while Europe as a whole may possibly stabilize its carbon emissions, this is clearly only the beginning of the effort needed to deal with climate change (EEA, 1995). Many other countries are having serious difficulties meeting their stabilization targets under the Framework Convention on Climate Change, and some decided to opt out of the Kyoto Protocol. Negotiations for the next stage in global action on climate change are under way, but the meeting of the parties to the UNFCCC in Copenhagen in December 2009 failed to make much progress.

As a result, carbon dioxide emissions rose 4.5% in 2004 to 27.5 billion tonnes, 26% higher than in 1990. China and India have doubled CO2 production since 1990. The US, the world's greatest emitter, increased by 20% and Australia by 40%. In 2004, the US released 5.8 billion tonnes of CO2, China 4.5 bt, Europe 3.3 bt, and India 1.1 bt. Clearly the political will to control greenhouse gases is lacking in most countries. For example, oil provides 40% of the world's primary energy, and world consumption of oil is increasing at 1.1%/year, with the wealthy (OECD) countries increasing at 1.3% per year, Latin America 2.8%, India 5.4% and China 7.5%. From 2001-2020, world oil consumption is predicted to rise 56%. Coal generates even more carbon dioxide per unit of energy, and coal consumtion for electricity generation is also projected to increase in those countries which depend on it. 25% of global CO2 emissions come from coal-fired power stations, and China plans to build 560 new coal-fired power plants and India 213. Declining fossil fuel reserves will raise prices and force an eventual reduction in emissions, but not before the damage is done. See Energy.

A good recent review of the scientific and political dimensions of the climate change debate is given by Dressler and Parson (2006).

Ethics and climate change


AtKisson, Alan. 1997. Personal communication based on briefing from Richard Barber, 24 November 1997.

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Bindoff, Nathan L., and J.A. Church. 1992. "Warming of the water column in the Southwest Pacific Ocean." Nature 357:59-62.

Bryden, Harry et al. 2005. Nature, 2005. Reviewed in Ian Sample, "Gulf Stream losing its zing," Guardian Weekly, 9-15 December 2005, p. 21.

Cane, Mark A., Gidon Eshel and R. W. Buckland. 1994. "Forecasting Zimbabwean maize yield using Eastern Equatorial Pacific sea-surface temperature." Nature 370:204-205. July 1994.

Dallimore, Scott R., and Timothy S. Collett. 1995. "Intrapermafrost gas hydrates from a deep core-hole in the MacKenzie Delta, Northwest Territories, Canada." Geology 23(6):527-530. June 1995.

Dessler, Andrew, and Edward Parson. 2006. The Science and Politics of Global Climate Change: A guide to the debate. Cambridge University Press, Cambridge.

EEA. 1995. Europe's Environment 1995. European Environment Agency, Copenhagen.

ENB. 1997. Report of the Meetings of the FCCC Subsidiary Bodies 20-31 October 1997. Earth Negotiations Bulletin, Vol 12, No. 66.

Grootes, P.M., M. Stuiver, J.W.C. White, S. Johnsen and J. Jouzel. 1993. "Comparison of oxygen-isotope records from the GISP2 and GRIP Greenland ice cores." Nature 366:552-554.

Hansen, Jim. 2006. Quoted in New Scientist, 4 February 2006, p. 7

Hecht, Jeff. 2006. "Losing the ground beneath their feet." New Scientist 18 February 2006, p. 8.

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IPCC. 2007. Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri, R.K. and Fleisinger, A. (eds.)], IPCC, Geneva, Switzerland. 104 p.

Japanese Maritime Safety Agency. 1995. Report, cited in Pearce, Fred. "Pacific plankton go missing". New Scientist, 8 April 1995.

Johannessen, Ola, et al. 1995. Nansen Environmental and Remote Sensing Centre, Bergen, paper presented at International Astronautical Congress, Oslo, October 1995. Cited in MacKenzie, Debora. "Polar meltdown fulfils worst predictions". New Scientist, 12 August 1995, p. 4.

Karl, Tom. 1998. (senior scientist at NOAA Climate Data Center) quoted in Sea Technology, February 1998, p. 7.

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Luckman, Adrian, et al. 2006. Geophysical Research Letters 33:L03503. reviewed in New Scientist 11 February 2006. p. 7.

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Pearce, Fred. 2006. "Arctic permafrost set to disappear over next century." New Scientist, 4 February 2006, p. 15.

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Roemmich, Dean, and John McGowan. 1995. "Climatic warming and the decline of zooplankton in the California Current." Science 267:1324-1326. 3 March 1995.

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Vaughan, David G., and C.S.M. Doake. 1996. "Recent atmospheric warming and retreat of ice shelves on the Antarctic Peninsula." Nature 379:328-331. January 1996.

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Wadhams, Peter. 1996. (Scott Polar Research Institute, and coordinator of European Sub-Polar Ocean Programme), on Odden feature, cited in Lean, Geoffrey. "Deep under the ice a chilling secret lies". The Independent, 18 February 1996.

WMO. 1995. Climate Information and Prediction Services (CLIPS). WMO - No. 832. World Meteorological Organization, Geneva.


Article last updated 27 March 2006

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