climate change and health
When glacial ice forms, small bubbles of air are trapped within, creating a continuous record of atmospheric composition. By drilling through the Antarctic ice sheet, it is possible to reconstruct atmospheric composition over the last 600,000 years. The present atmospheric carbon dioxide concentration has not been exceeded during the past 600,000 years, and possibly the past 20 million years.
Several lines of evidence confirm that the recent and continuing increase of atmospheric carbon dioxide content is caused by human carbon dioxide emissions, and
rising temperatures
Largely as a result of increasing atmospheric greenhouse gas concentrations, global mean temperatures have increased by 0.7˚C since around 1900. Over the past 30 years, global temperatures have risen rapidly and continuously (at around 0.2˚C per decade) to the warmest level reached in the current interglacial period, which began around 12,000 years ago.
Most climate model calculations show a doubling of pre-industrial levels of greenhouse gases is very likely to commit the earth to a rise of between 2˚C and 5˚C in global mean temperatures. This level of greenhouse gases will probably be reached between 2030 and 2060.
in particular fossil fuel burning. These human-induced carbon dioxide emissions enhance the already existing greenhouse effect, causing global warming and fundamental changes in climate.
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Long-range climate forecasts lack detail because of the non- linear chaotic nature of climate systems. Warming is projected to be greatest over land and at most high northern latitudes, with Arctic late-summer ice disappearing almost entirely by the latter part of the 21st century.
why the controversy?
Climate change studies in the late 20th century were often
highly controversial, partly because some oil and other commercial companies, to protect their perceived interests, funded campaigns against the results of climate research. Climate research in the 21st century has made considerable advances.
The Intergovernmental Panel on Climate Change (IPCC) comments that warming of the global climate system is unequivocal, in their latest assessment report. This is now evident from observations of increases in global average air and ocean temperatures, 1 widespread melting of snow and ice, and rising global average sea level. The report further comments that continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.
Clearly carbon dioxide emissions have to be reduced, but ‘by how much?’ is a recent source of controversy. A 50% reduction of global emissions below 1990 levels by 2050, widely considered to be the
nucleus christmas ‘08
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