Indications of Climate Change

The 2007 report of the Intergovernmental Panel on Climate Change (IPCC) a global body which collates and assesses the results of international climate research, identifies several indicators of climate change on a global scale:

• global average temperatures have risen by nearly 0.8 ºC since the late 19th century
• global temperatures have risen fastest in the past 25 years, by about 0.5 ºC
• 11 of the warmest 12 years ever recorded occurred since 1994
• reduction in the extent of sea-ice could result in the Arctic being ice-free in summer by 2013
• glaciers are retreating on all continents
• sea level has risen by 3.1mm per year since 1993 due to thermal expansion of water and ice melt
• the frequency of extreme rainfall events has increased
• tropical droughts have become, on average, longer and more intense

In Northern Ireland (.PDF 1.20 Mb), climate data recorded at Armagh Observatory since 1841 shows that:

• mean annual temperature has been increasing steadily since the early 1980s
• the number of extremely hot days (over 18ºC) per year has increased since 1980 while the number of extremely cold (below 0ºC) days has declined
• the number of days with snow has declined dramatically since 1980

Predictions of future climate have been made by using computer simulations which take into account all the various factors known to affect weather. These can never be wholly accurate but the best of these models give results that correspond well with what is now being observed. Modelling results for Northern Ireland made by the UK Climate Impacts Programme (UKCIP) in 2002 predict that, by 2080, mean temperatures will rise by 1ºC – 3.5º, summer rainfall will decline by 20% - 50%, winter rainfall will increase by 10% - 25% and snowfall will decline by between 40% and 100%.

Extreme weather events such as floods, droughts and heatwaves will become more frequent. Sea-level may rise by 9cm – 69cm. A temperature rise of only 3ºC may not seem dramatic but an increase of 1ºC is the climatic equivalent of moving 250km to the south. An increase of 1ºC would therefore give Belfast a climate similar to that of County Cork or Devon.