Climate Change
There is a lot of information out there about climate change and its effects. But what are the facts and what are opinions? Polarventure hopes to distinguish the fact from the fiction.
The following information has been edited from the Royal Society's document 'A guide to facts and fictions about climate change' and draws upon the work of the Intergovernmental Panel on Climate Change (IPCC).
1. Climate change has happened throughout the Earth's history.
This statement is true and according to natural historians there are also periods in the Earth's history when the climate changed. dramatically. When this happens species cannot adapt quick enough and this causes extinctions.It has been said that the rate at which species are becoming extinct that we are in the midst of the sixth mass extinction in the earth's history.
2. Not all scientists believe that climate change is a problem.
There are some differences of opinion among scientists about some of the details of climate change and the contribution of human activities, such as the burning of fossil fuels. Researchers continue to collect more data about climate change and to investigate different explanations for the evidence.
However, the overwhelming majority of scientists who work on climate change agree on the main points, that climate change is a problem and that humans have had a significant role to play even if there is still some uncertainty about particular aspects, such as how the concentration of greenhouse gases in the atmosphere will change in the future.
3. There is little evidence that global warming is happening or, if it is happening, it is not very much. Some parts of the world are actually becoming cooler. Increased urbanisation could be responsible for much of the increase in observed temperatures. Satellite temperature records do not show any global warming. If there has been global warming recently, it would not even be a unique occurrence within the past 1000 years. Europe has been much warmer in the past.
Few scientists dispute that the global average temperature has been rising for at least a century. The IPCC 2001 report concluded, based on worldwide measurements, that the average surface temperature of the Earth had risen by 0.6 centigrade degrees (+/-0.2°C) during the 20th century. The IPCC found that, in terms of the global average temperature, the 1990s were very likely (a 90-99% chance) to have been the warmest decade since records began in 1861, and that 1998 was the warmest year.Furthermore, the increase in surface temperature during the 20th century in the Northern Hemisphere was likely (a chance of 66 to 90%) to have been greater than for any other century for the last 1000 years.
In the journal Nature a scientist named Moberg concluded that he has found no evidence that over the last 2000 years there has been a warmer period that the one we are now living in since 1990.
4. The Earth is getting hotter, but not because of emissions of greenhouse gases from human activities. Carbon dioxide makes up such a tiny fraction of the atmosphere that even if it doubled it would make little difference to the climate. Variations in the sun are more likely to be the cause of climate changing than increases in greenhouse gases.
About half of the solar energy entering the top of the Earth’s atmosphere eventually reaches the surface where it is absorbed. Much of the solar energy is absorbed by the Earth’s surface and then released as infra-red radiation, some of which is absorbed by greenhouse gases such as water vapour, carbon dioxide and methane. The greenhouse gases act like a blanket over the surface of the Earth, keeping it around 20 centigrade degrees warmer than it otherwise would be, which is a phenomenon known as ‘the greenhouse effect’.
Increases in the concentrations of greenhouse gases in the atmosphere enhance the greenhouse effect and, on average, lead to further warming. It has been long established that carbon dioxide strongly absorbs infra-red radiation. The IPCC 2001 report pointed out that carbon dioxide is 'the dominant human-influenced greenhouse gas', and is responsible for more than half the warming due to changes in atmospheric concentrations.
Based on direct analysis of gases found trapped in cores of polar ice, it is known that the atmospheric concentration of carbon dioxide for several thousands of years before 1750 was about 280 parts per million. Between 1750 and 2000, during which industrialisation has occurred, the concentration rose by about 31%. The IPCC report noted that the current concentration of carbon dioxide in the atmosphere has not been exceeded during the past 420,000 years and that 'the rate of increase over the past century is unprecedented, at least during the past 20,000 years'.
A recent study by Solanki and others, published in the journal Nature, found that the level of solar activity during the past 70 years has been 'exceptional' when considered over the period of the last 11,400 years. However, they concluded that 'although the rarity of the current episode of high average sunspot numbers may indicate that the Sun has contributed to the unusual climate change during the twentieth century, we point out that solar variability is unlikely to have been the dominant cause of the strong warming during the past three decades'.
Misleading arguments 5. Scientists have been exaggerating the evidence by claiming that individual extreme weather events have been caused by climate change. The recent flooding in the UK in places like Boscastle and Carlisle would have happened anyway, and the frequency of hurricanes hitting the Caribbean and Atlantic coast of the United States is no different than in the past. Even if they appear to be more severe, this is only because more people are living in places that are affected by natural extreme weather events.
In general, it is not possible to state categorically that individual weather events are due to changes in climate, and reputable scientists are extremely cautious about such claims. However, there is a link, albeit complex, between changes in climate and regional and local weather events, including extreme ones. Changes in the global climate can be expected to lead to patterns of local and regional weather events, particularly extreme ones. While scientists may be able to estimate the change in the likelihood of such events because of climate change, they cannot predict individual events.
In 2002, Palmer and Räisänen reported in the journal Nature the results of analyses of 19 global climate model simulations that indicate 'the probability of occurrence of a very wet winter over the UK is estimated to increase by a factor of 5 over the next 50-100 years, due to man’s effect on climate'. In this case, very wet winters are characterised by significantly above average seasonal rainfall. These models also imply 'an increased risk of flooding in Bangladesh' over the same period.
In the journal 'Nature' in 2004, It was noted that the summer of 2003 was probably the hottest in Europe since at least 1500. It has been estimated that the heatwave caused 22,000- 35,000 additional deaths. It was not possible to meaningfully determine whether the heatwave was due to increased atmospheric concentrations of greenhouse gases. However, they concluded from an analysis of instrument records since 1851 that 'it seems likely that past human influence has more than doubled the risk of European mean summer temperatures as hot as 2003, and with the likelihood of such events projected to increase 100-fold over the next four decades'
The IPCC 2001 report acknowledged that it was not possible to tell what impact climate change would have on some individual local weather events.
Misleading arguments 6. There is conflicting evidence about whether the ice at the poles is melting and, in fact, it is actually becoming thicker in Antarctica.
The IPCC 2001 report indicated that in 2000 Arctic ice had thinned overall by 40% in the late summer and early autumn in the past few decades, and decreased in extent by 10 to 15% since the 1950s in the spring and summer. There has also been a widespread retreat of non-polar glaciers. However, there was no noticeable change in the overall extent of Antarctic sea ice between 1978 and 2000.
The models reported by the IPCC showed that glaciers would continue to retreat with rises in global average temperatures. The situation is very complex, 'the Antarctic ice sheet is likely to gain mass because of greater precipitation, while the Greenland ice sheet is likely to lose mass because the increase in runoff will exceed the precipitation increase.' Looking further into the future, larger changes in the ice sheets may begin to occur. The IPCC 2001 report also warned that a local average warming by 3 centigrade degrees would lead, over a thousand years, to 'virtually a complete melting of the Greenland ice sheet with a resulting sea level rise of about 7 m [metres]'. The report also warned that the West Antarctic Ice Sheet may start to break up if temperatures continue to climb.
A recent paper by Shepherd and others published in the journal Science in 2003, suggested that the Larsen Ice Shelf in Antarctica has begun to break-up over a very short period due to a sustained period of thinning of the ice. They concluded that 'enhanced ocean-driven melting may provide a simple link between regional climate warming and the successive disintegration of sections of the Larsen Ice Shelf'.
Misleading arguments 7. There is little evidence of a rise in sea level due to global warming. There is no correlation between rises in climate temperature and sea levels. There has been no consistent trend this century, with sea level rising in some places but not in others. Even if sea level is rising it has nothing to do with global warming and is actually due to the fact that southern England is sinking due to the bending of the Earth’s crust.
The IPCC 2001 report found that average sea level around the world increased at a rate of 0.1 to 0.2 centimetres per year during the 20th century. This had been caused by a combination of the thermal expansion of seawater (ie the volume of a fixed mass of water increases as it is heated) and the melting of land ice. The report acknowledged that there had not been a significant acceleration in the rate of sea level rise during the 20th century, and that this was 'not inconsistent with model results'. According to the IPCC models, global average sea levels would rise by 3 to 14 centimetres by 2025 compared to 1990, and by 9 to 88 centimetres by 2100, although the amount of sea level rise would vary very significantly between regions. The rise would be due to thermal expansion and the melting of glaciers and ice caps.
As Shennan and Horton reported in the Journal of Quaternary Research in 2002, sea levels around Great Britain have been influenced for instance by a phenomenon known as isostatic rebound. During the last Ice Age, Britain was covered by ice sheets as far south as the Thames Estuary. The ice sheet caused the land beneath it to sink, while the land in front of it, in southern England bulged up. When the ice sheet retreated after the end of the Ice Age, the land that had been beneath it started and continues to rise slowly, while the land in the bulge is sinking slowly. Other factors, such as the compaction of sediments, also cause changes in land movements. Shennan and Horton found that, overall, central and western Scotland are rising at about 1.6 millimetres per year while the south-west England is sinking by about 1.2 millimetres per year.
Misleading arguments 8. There is no evidence that climate change will be bad for people. In fact, warmer weather will actually be good for those people who live in cold countries. Climate change may make some places like Russia warmer and more productive places to live. A warmer climate will be good for the UK’s economy, with more tourists and better wine-producing conditions. Increasing levels of carbon dioxide would produce a rise in plant productivity and crop yields. Surely we should let the benefits and costs of climate change even themselves out.
The IPCC models acknowledge that some parts of the globe would benefit, at least in the short-term, from climate change. Some high northern latitudes could experience less extreme cold and a longer growing season for crops. In addition, the higher concentrations of carbon dioxide in the atmosphere will boost growth of some important crops, and given adequate water and nutrients, will bring higher yields.
However, the IPCC models indicate that 'the larger the changes and rate of change in climate, the more the adverse effects predominate'. These adverse effects would be most severe in the tropics and subtropics. The IPCC pointed out that 'reducing the projected increase in climate extremes is expected to benefit all countries, particularly developing countries, which are considered to be more vulnerable to climate change than developed countries'.
While some commentators in the media have imagined that climate change will bring benefits to the UK, such as 'better wine-producing conditions', they do not appear to take into account the significant problems that we will face through an increase in the likelihood of flooding in some areas, a reduction in the availability of fresh water in others, and more threats to sea defences due to sea level rise in many low-lying areas,
The focus on the UK also ignores the misery and suffering that will increase for the world’s poorest and most vulnerable people.
In most of the IPCC models, overall crop yields would decrease as temperatures rise. The report warned that 'warming of a few °C or more is projected to increase food prices globally, and may increase the risk of hunger in vulnerable populations'. Those parts of the world already experiencing water shortages would find their problems worsen with climate change, although some places may see an overall increase in rainfall.
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- 1. Climate change has happened throughout the Earth's history.
- 2. Not all scientists believe that climate change is a problem.
- 3. There is little evidence that global warming is happening or, if it is happening, it is not very much. Some parts of the world are actually becoming cooler. Increased urbanisation could be responsible for much of the increase in observed temperatures. Satellite temperature records do not show any global warming. If there has been global warming recently, it would not even be a unique occurrence within the past 1000 years. Europe has been much warmer in the past.
- 4. The Earth is getting hotter, but not because of emissions of greenhouse gases from human activities. Carbon dioxide makes up such a tiny fraction of the atmosphere that even if it doubled it would make little difference to the climate. Variations in the sun are more likely to be the cause of climate changing than increases in greenhouse gases.
- 5. Scientists have been exaggerating the evidence by claiming that individual extreme weather events have been caused by climate change. The recent flooding in the UK in places like Boscastle and Carlisle would have happened anyway, and the frequency of hurricanes hitting the Caribbean and Atlantic coast of the United States is no different than in the past. Even if they appear to be more severe, this is only because more people are living in places that are affected by natural extreme weather events.
- 6. There is conflicting evidence about whether the ice at the poles is melting and, in fact, it is actually becoming thicker in Antarctica.
- 7. There is little evidence of a rise in sea level due to global warming. There is no correlation between rises in climate temperature and sea levels. There has been no consistent trend this century, with sea level rising in some places but not in others. Even if sea level is rising it has nothing to do with global warming and is actually due to the fact that southern England is sinking due to the bending of the Earth’s crust.
- 8.There is no evidence that climate change will be bad for people. In fact, warmer weather will actually be good for those people who live in cold countries. Climate change may make some places like Russia warmer and more productive places to live. A warmer climate will be good for the UK’s economy, with more tourists and better wine-producing conditions. Increasing levels of carbon dioxide would produce a rise in plant productivity and crop yields. Surely we should let the benefits and costs of climate change even themselves out.
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