Is global warming for real? Is it natural, or human-caused? Who will benefit from its effects? Suffer? The scientific debate on climate change remains as political as ever
While policymakers mull over controlling emissions of greenhouse gases (ghgs), scientists are still squabbling about global warming. Some assert it is not happening. Others avow it is natural, not human-caused. They cite cosmic influences as key to climate change.
Attempts have also been made to refute the impacts of rising ghg levels. A June 2004 Nature paper by Raymond T Pierrehumbert of the University of Chicago, usa , states that even if carbon dioxide (co2) concentration is 550 times the present level (about 368 parts per million), de-glaciation (complete melting of ice sheets) is unlikely to happen. Such refutation flies in the face of the path-breaking report on climate change science finalised in January 2001 by the Intergovernmental Panel on Climate Change (ipcc) -- the premier organisation on climate change established in 1998 by the World Meteorological Organisation (wmo) and the United Nations Environment Programme.
The ipcc report took 122 lead authors to marshal submissions from 515 other contributors. To date, the report is a key reference for climate change scientists, policymakers as well as critics. The report clearly states that average surface temperatures have increased over the 20th century by about 0.6 c and most of this increase is human-caused. 1990s was the warmest decade and 1998 the warmest year since 1861 (the year temperatures began to be recorded).
Scientific literature published after 2001 supports the ipcc findings. The latest proof comes from a December 15, 2004 wmo report. "The global mean surface temperature in 2004 is expected to be 0.44 c more than the 1961-1990 annual average (14 c )," it states. This means 2004 is the fourth warmest year since 1861, a trifle behind 2003 (+0.49 c).
ipcc predicts that 1990-2100 global average surface temperature may increase by 1.4-5.8 c . This implies that the impacts of global warming would be more severe than what they are at present. Already, according to ipcc, there has been a decrease of about 10 per cent in the extent of snow cover since the late 1960s. Analysis of tide 'gauge' data shows that global average sea level rose between 0.1 and 0.2 metres (m) during the 20th century. It is projected to rise by 0.09 to 0.88 m between 1990 and 2100. For 1990-2025 and 1990-2050, ipcc projects a rise of 0.03 to 0.14 m and 0.05 to 0.32 m respectively.
In this context, climate mitigation is imperative. The ipcc report even gives dire warnings about the impacts of global warming, such as large-scale flooding and frequent storms. The only way out is to reduce ghg emissions by 50-70 per cent below 1990 levels. However, this 'essential need' may always remain confined to the realm of negotiations, or inaction.
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