The Impacts and Costs of Climate Change Page: ii

                                
The Impacts and Costs of Climate Change
Above 2'C temperature increase, the vast majority of market impacts are predicted to be negative and
most regions will suffer adverse affects from climate change. Risks from large-scale discontinuities
become significant above a 3'C temperature change.
This information was updated in the recent 'Stabilisation 2005', an International Symposium on the
Stabilisation of Greenhouse Gases, held in February 2005. The conference noted changes of up to 1 C
might be beneficial for a few regions and sectors such as agriculture in mid to high latitudes. A
number of new impacts were identified. One example is the recent change in the acidity of the ocean,
reducing its capacity as a carbon sink. The conference highlighted that a global temperature rise of
about 1.5'C may be a threshold that triggers melting of the Greenland ice-cap. The conference
concluded that serious risk of large scale, irreversible system disruption, such as changes to the
thermohaline circulation, reversal of the land carbon sink and possible destabilisation of the Antarctic
ice sheets is more likely above 3C.
The findings of this review are summarised in the table below.
Summary of literature on climate impacts with different temperature stabilisation scenarios.
Within 2C                   >2C to 2.50C                       >3C
Health        Estimated an average global  A rise of 2.3C by 2080 puts up to  A rise of 3.3C by 2080 would put
temperature rise > 1.20C will  270 million at risk from malaria  up to 330 million at risk from
increase premature mortality  (IS92a S>1000).               malaria (IS92a unmit).
by several hundred thousands
excluding extreme events like
heat waves.
Ecosystems    Up to 1C above pre-       A rise of 1-20C above pre-      Rise of> 20C above pre-industrial
industrial levels up to 10% of  industrial levels will shift up to  levels, global share of ecosystems
ecosystem areas worldwide   15-20% of ecosystem areas       shifting due to climate change
will shift.                 worldwide.                      likely above 20%, and much more
in some regions. Global losses of
coastal wetlands may exceed 10%.
Agriculture   The EU (and US) yields     Heat stress likely to affect    Higher average temperatures of
increases for up to 20C     subtropics/tropics for 1.70C    2.50C in 2080 could result in 50
temperature rise, but beyond  temperature increase,         million additional people at risk of
this decline.                                               hunger. With a 3C rise a group of
developing countries with a
population of 2 billion will see the
food deficit double.
Water         For many regions under     Above 2 to 2.50C global average  Above 2.5C warming the level of
water stress, global mean   temperature increase it is projected  risk begins to saturate in the range
temperature increases above  that additional 2.4 to 3.1 billion  of 3.1- 3.5 billion additional
around 1.5C lead to        people will be at risk of water  persons at risk.
decreases in water supply.  stress
Additional number of people
in water shortage regions in
the range 400-800 million for
around a 1C warming.
Major         At 1.5oC onset of complete  Above 2oC risk of major        Above 3.C risk of major
events       melting of Greenland Ice:   catastrophic events. Between 2oC  catastrophic events very
when complete 7m additional  and 4.5oC potential to trigger  significant. Over 4oC the
sea level rise.             melting of the West Antarctic Ice  probability of thermohaline
Sheet eventually raising sea levels  shutdown up to 50% or above.
by a further 5-6m.
We highlight further work in this area, providing disaggregated impacts for different stabilisation

targets, is one of the major research recommendations for the future.

AEA Technology Environment, August 2005