The greenhouse effect is the process by which the atmosphere traps some of the sun’s energy, warming the Earth and moderating our climate. A human-driven increase in ‘greenhouse gases’ has enhanced this effect artificially. These greenhouse gases include carbon dioxide, produced by burning fossil fuels and through deforestation, methane, released from agriculture, animals and landfill sites, and nitrous oxide, resulting from agricultural production plus a variety of industrial chemicals.

Every day we damage our climate by using fossil fuels (oil, coal and gas) for energy and transport. As a result, climate change is already impacting on our lives, and is expected to destroy the livelihoods of many people in the developing world, as well as ecosystems and species, in the coming decades. We therefore need to significantly reduce our greenhouse gas emissions .

Last year, the UN Intergovernmental Panel on Climate Change (IPCC) set out an overwhelming body of scientific evidence which put the reality of human-induced climate change beyond any doubt. During 2007 the IPCC was also awarded the Nobel Peace prize in clear recognition that climate change poses a major challenge to the security of mankind in the 21st century1.

Involving over 3,800 scientists from over 150 countries and six years of work, the IPCC Fourth Assessment Report, published in instalments between January and November 2007, reviewed and analysed scientific studies published up to the end of 2006, and in a few cases, to early 2007. Since the publication of this key report, scientific research on climate change and its impacts has continued and new studies are revealing that global warming is accelerating, at times far beyond forecasts outlined in earlier studies included the Fourth Assessment Report.

New numerical modelling studies also provide more detailed indications of the impacts to come if warming continues. According to the IPCC, the world’s temperature is expected to increase over the next hundred years by up to 5.8°C . This is much faster than anything experienced so far in human history. The goal of climate policy should be to keep the global mean temperature rise to less than 2°C above pre-industrial levels. At 2°C and above, damage to ecosystems and disruption to the climate system increases dramatically.

Global carbon dioxide (CO2) emissions released as a consequence of human activity have been accelerating , with their growth rate increasing from 1.1% per year between 1990 and 1999, to more than 3% per year between 2000 and 2004. The actual emissions growth rate since 2000 was greater than any of the scenarios used by the IPCC in either the Third or Fourth Assessment Reports. Over the past 15 years, about half the CO2 emissions arising from human activity have been absorbed by land and ocean. However, the capability of these natural sinks is declining at a greater rate than forecast in earlier studies. This means that more of the CO2 emitted from human activities will stay in the atmosphere and contribute to global warming.

A re-examination of the climate impacts reported in the Fourth Assessment Report indicates that 80% cuts in global greenhouse gas emissions are needed by 2050 to keep global average temperature rise below 2°C – and to limit climate impacts to ‘acceptable’ levels. Such a cut would stabilise atmospheric greenhouse gas concentration at 400-470 parts per million carbon dioxide equivalents. However, even with an 80% emissions cut, damages will be significant, and much more substantial adaptation efforts than those currently planned will be required to avoid much of the damage.

Important aspects of climate change seem to have been underestimated and the impacts are being felt sooner. For example, early signs of change suggest that the less than 1°C of global warming that the world has experienced to date may have already triggered the first tipping point of the Earth’s climate system – the disappearance of summer Arctic sea ice.

This process could open the gates to rapid and abrupt climate change, rather than the gradual changes that have been forecast so far. The implication of this recent evidence is that our mitigation and adaptation responses to climate change need to be even more rapid and ambitious. This means that global emissions will have to peak and start to decline by the end of the next decade at the latest.

Past and future CO2 concentrations. Since pre-industrial times, the atmospheric concentration of greenhouse gases has grown significantly. Carbon dioxide (CO2) concentration has increased by about 31%, methane concentration by about 150%, and nitrous oxide concentration by about 16% (Watson et al 2001). The present level of carbon dioxide concentration (around 375 parts per million) is the highest for 420,000 years, and probably the highest for the past 20 million years.

Temperature trends and projections. The global average surface temperature has increased over the 20th century by about 0.6 degrees Celsius. This increase in temperature is likely to have been the largest for any century in the last 1000 years. Evidence from tree ring records, used to reconstruct temperatures over this period, suggests that the 1990s was the warmest period in a millennium. It is very likely that nearly all land areas will warm more rapidly than the global average, particularly those at high northern latitudes in the cold season. There are very likely to be more hot days; fewer cold days, cold waves, and frost days; and a reduced diurnal temperature range.

Climate change is already harming people and ecosystems . Its reality can be seen in disintegrating polar ice, thawing permafrost, dying coral reefs, rising sea levels and fatal heat waves. An average global warming of 2°C threatens millions of people with an increased risk of hunger, malaria, flooding and water shortages.

Since we began recording temperature in the 1850s the ten warmest years worldwide have occurred in the past eleven years and 2006 marked the warmest year in the UK and the Netherlands and the warmest autumn in Denmark, Norway, Switzerland and Germany. Apart from heat waves, forest fires and prolonged droughts, mainly in Southern Europe, climate change has led to more extreme precipitation in Northern Europe, which has the potential to unleash devastating floods.

Never before has humanity been forced to grapple with such an immense environmental crisis. If we do not take urgent and immediate action to stop global warming, the damage could become irreversible . This can only happen through a rapid reduction in the emission of greenhouse gases into the atmosphere.

According to scientists, in order to stay below 2°C global warming compared to pre-industrial temperatures – the objective endorsed by the European Union – an overall greenhouse gas emissions reduction of 30% by 2020 and 80% by 2050 compared to 1990 is needed in all developed nations.

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