From The Weather Makers (Tim Flannery, 2005) pp164-5
A number of climate groups often at the request of governments needing advice on how to prepare themselves have produced computer-based projections for various regions of Earth and for time scales as short as a few decades. Three examples of .such studies help provide a taste of the numerous regional predictions that abound. It’s worth keeping in mind, however, that many climatologists question the usefulness of such reports.
Some of the most sophisticated regional predictions are those produced by the Hadley Centre for the climate of the United Kingdom from the 2050s to the 2080s. They assume the presence of a range of greenhouse gas emissions from low to high. Low means strenuous measures to reduce CO2 emissions would have been successfully implemented, and luck with feedback loops; high means business as usual and bad luck with feedback loops.
With all scenarios they discovered that by 2050 human influences on the climate will have surpassed all natural influences. In other words, there will be no more climatic ‘acts of God’, only human-made climate disasters. They predict that snow cover will decrease by up to 80 per cent near the British coast, and up to 60 per cent in the Scottish highlands. Winter rainfall is predicted to increase by up to 35 per cent, with more intense rainfall events, while summer rainfall will decrease, and one summer out of three will be ‘very dry’. An event akin to the severe summer of 1995 (which had seventeen days over 25°C and four days over 30°C) may recur twice per decade, while the great majority of years will be warmer than the record-breaking 1999.
The changes felt over the European landmass will be more extreme than the increase in the global average. Indeed, a global rise in surface temperature of just 2°C would bring a temperature rise to all of Europe, Asia and the Americas of 4.5 degrees. For Britain, this means a more Mediterranean-like climate and, as some newspapers put it, ‘the end of the English garden’. More important are the challenges it throws up for matters such as water security, flood mitigation and human health.
In 2003 and 2004 two further regional studies, prepared by scientists from Stanford and the University of California at Los Angeles, focused on climate impacts for California. They postulated that global warming would bring much hotter summers to the state and a depleted snowpack, threatening both water supplies and health. By the end of the century, heatwaves in Los Angeles would be two to seven times as deadly as today, snowpacks would decline by half or more, and three-quarters to nine-tenths of all of California’s alpine forests would be lost.
The third example focuses on the state of New South Wales, with predictions made by Australia’s leading science research body, the CSIRO. The time scale used here is short only three decades in some instances and it utilises twelve separate climate simulations that deliver a wide range of possibilities. These include temperature increases across the state of between 0.2 and 2.1°C while the number of cold spells, and thus frosts, will reduce. The number of very hot days (above 40’C) will increase, as may winter and spring droughts, extreme rainfall events and wind speeds, and there will be changes in wave patterns and possibly the frequency of storm tides.
In reading regional reports it is evident that the shorter the time scale the less certain are the predictions; conversely, the longer the time scale and the larger the region involved, the more they resemble global models, which are our best source of information. There is one other very important reason why short-term studies are not so significant. The gas is already in the air and right now we have no way of getting it out. This means that the course of climate change is set for at least the next several decades.
Tgk1946's Blog 