The science of climate change
As through much of its history, the Earth's climate is changing as a result
of natural processes. Most of the warming in recent decades is very likely to
be caused by greenhouse gas emissions generated by human activity. These changes
could have an adverse impacts on the global economy and environments and societies
worldwide.
According to Inter-Governmental Panel on Climate Change (IPPC) which published
its Fourth Assessment Report. IPPC Working Group 1, during 2007, global atmospheric
concentrations of carbon dioxide, methane and nitrous oxide have increased markedly
as a result of human activities since 1750 and now far exceed pre-industrial
values determined from ice cores spanning many thousands of years.
The Fourth Assessment Report draws attention to :
Warming: Over the past 50 years the rate of warming has been nearly twice as
fast as it was over the past 100. Sea level rise: The global average sea level
has risen at some 1.8 mm per year between 1961 and 2003. From 1993 to 2003,
the rate increased to 3.1 mm per year and the total rise during the 20th century
is estimated to be between 0.12 and 0.22 m.
Drought: Since the 1970s, higher temperatures and decreased rainfall have led
to severe droughts, particularly in the tropics and subtropics. Extreme weather:
Heavy rainfall has become more common over most land areas and intense tropical
cyclone activity has been identified in the North Atlantic that has been increasing
since 1970, in association with increased tropical sea-surface temperatures.
The report also shows that depending on the rate of greenhouse-gas emissions,
the climate might change over the course of the next century. It also suggests
that global surface temperatures are likely to increase by about 0.2°C per
decade over the next two decades.
The average rise in sea levels is likely to be from 28 to 43 cm by the end
of the century.
In October 2006 Sir Nicholas Stern (Head of the Government Economic Service
and former World Bank Chief Economist) published his independent review on the
Economics of Climate Change (Stern 2007). According to him, there is still time
to avoid the worst impacts of climate change, if concerted action is taken now
- Action to reduce greenhouse-gas emissions avoiding worst impacts of climate
change was calculated to cost a maximum of around 1 per cent of global GDP each
year.
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