CABI Blog

Image credit: NASA Goddard Space Flight Center.

NASA satelite pictures and a BBC News item on the latest data from the
Norwegian Polar Institute (NPI) showed that the Arctic sea ice has
thawed to record levels this year. It is well known that the Arctic ice
thaws annually during the summer months, when the temperature is above
freezing, and forms again in the winter, but lately more ice is melting
each year and the floating ice is at its smallest since monitoring began
more than 30 years ago. What are the causes and implications?

The line on the above image shows the average minimum
extent from the period 1979-2010, as measured by
satellites. NASA says that a 13% decline
per decade in the minimum summertime extent of the sea ice has been observed over the last three decades. The thickness of the
sea ice cover also continues to decline.

Scientist from NPI has been gathering and examining data from their Norway's
Arctic research station at Ny-Alesund on Svalbard, since the beginning
of the 1990s, using satellites and a range of different techniques, both
old and new. They have seen a greater change than they could even imagine 20 or even 10 years ago, said their international director, Kim Holmen.

The BBC news article says: “the most cautious forecasts say that the
Arctic might become ice-free in the summer by the 2080s or 2090s, but
that recently many estimates for that scenario have been brought
forward.”

The Causes

The main cause for the accelerated melting of Artic sea ice is global
warming, which is caused mainly by greenhouse gases (GHG) emissions. In its
report ‘State of the Climate: Global Analysis, July 2012’ the National
Oceanic and Atmospheric Administration (NOAA) showed that the average
combined global land and ocean surface temperature for July 2012 was
0.62°C above the 20th century average of 15.8°C, making this the fourth
warmest July since records began in 1880. The global average land
surface temperature for July 2012 was the third warmest on record, at
0.92°C above average. This figure was even higher (1.19°C) when
considering the Northern Hemisphere separately.

Things can only get worse, it seems, if the outcome of the interim
climate talks which concluded in Bangkok, Thailand, last Wednesday is
anything to go by. According to various news reports from participant
observers of the talks, none of the 190 nations involved in the
talks made new commitments regarding emissions reduction, as promised
in previous climate meetings.

An article from the Energy and Environment Management (EEM) webpage
said that US negotiators "stunned” delegates when they called for any
new climate treaty to be "flexible" and "dynamic" rather than legally
binding. These climate talks in Bangkok were intended as a preparation
for the major UN end-of-the-year climate change meeting, which this
year will take place in Doha, Qatar, from 26 November to 7 December
2012.

A report by the UN Environment Programme (UNEP) showed that several
rich nations will not meet their existing pledges to cut GHG emissions
by the end of the decade and even if they did, GHG emissions would still
be 20% above what is needed to keep global temperature increase below
2°C. This means stronger commitments from rich and developing nations is
still very much needed, otherwise a 3.5°C temperature increase is more likely.

The Implications

The Norwegian researchers suggested that a large reduction in sea ice
is likely to have an impact on the path of the jet stream (the high
altitude wind that guides weather systems such as storms) and that these
changes will be observed across and beyond Europe.

This happens because of the albedo effect, i.e. white surfaces such as a
frozen Arctic sea has high albedo or reflecting power and reflect most of the sunlight reaching it, whereas darker surfaces such as
deep water has lower reflecting power and absorbs more of the sunlight reaching it. This means when the Arctic is ice free it
will absorb more sunlight and the warm sea in turn will influence wind
systems and precipitation patterns.

Links to references

David Shukman’s coverage of the Arctic Sea thaw story on the BBC News online.

NASA satelite images of shrinking Arctic sea ice.

‘State of the Climate : Global Analysis, July 2012,’ from the  National Oceanic and Atmospheric Administration (NOAA).

Energy and Environment Management News article.

UNEP Emissions Gap Report.

The CABI internet resource Environmental Impact is a comprehensive source of bibliographic
information  on climate change and other influences of humans on the
biosphere, which also covers other aspects of man's damage to the environment
such as pollution, deforestation, desertification and habitat loss.