Cement, Energy and Environment

roughly twice the surface value. However, the temperature data from balloons give the opposite result: no increasing warming, but rather a slight cooling with altitude. • Temperature records in Greenland and other Arctic areas reveal that temperatures reached a maximum around 1930 and have decreased in recent decades. Longer-term studies depict oscillatory cooling since the Climatic Optimum of the mid- Holocene (-9000-5000 years BP), when it was perhaps 2.5°C warmer than it is now. • The average temperature history of Antarctica provides no evidence of twentieth century warming. While the Antarctic peninsula shows recent warming, several research teams have documented a cooling trend for the interior of the continent since the 1970s. Chapter 4. Observations: Glaciers, Sea Ice, Precipitation, and Sea Level • Glaciers around the world are continuously advancing and retreating, with a general pattern of retreat since the end of the Little Ice Age. There is no evidence of a increased rate of melting overall since C0 2 levels, suggesting C0 2 is not responsible for glaciers melting. • Sea ice area and extent have continued to increase around Antractica over the past few decades. Evidence shows that much of the reported thinning of Arctic sea ice that occurred in the 1990s was a natural • • • consequence of changes in ice dynamics caused by an atmospheric regime shift, of which there have been several in decades past and will likely be several in decades to come, totally irrespective of past or future changes in the air's C0 2 content. The Arctic appears to have recovered from its 2007 decline. Global studies of precipitation trends show no net increase and no consistent trend with C0 2 , contradicting climate model predictions that warming should cause increased precipitation. Research on Africa, the Arctic, Asia, Europe, and North and South America all find no evidence of a significant impact on precipitation that could be attributed to anthropogenic global warming. The cumulative discharge of the world's rivers remained statistically unchanged between 1951 and 2000, a finding that contradicts computer forecasts that a warmer world would cause large changes in global streamflow characteristics. Droughts and floods have been found to be less frequent and severe during the Current Warm Period than during past periods when temperatures were even higher than they are today. The results of several research studies argue strongly against claims that C0 2 -induced global warming would cause catastrophic disintegration of the Greenland and Antarctic Ice Sheets. In fact, in the case of Antarctica, they suggest just the opposite -i.e. , that C0 2 -induced global warming would tend to buffer the world against such an outcome. • The mean rate of global sea level rise has not accelerated over the recent past. The determinants of sea level are poorly understood due to considerable uncertainty associated with a number of basic parameters that are related to the water balance of the world's oceans and the meltwater contribution of Greenland and Antarctica. Until these uncertainties are satisfactorily resolved, we cannot be confident that short-lived changes in global temperature produce corresponding changes in sealevel. Chapter 5. Solar Variability and Climate Cycles • The IPCC claims the radiative forcing due to changes in the solar output since 1750 is +0.12 wm· 2 , an order of magnitude smaller than its estimate net anthropogenic forcing of+1 .66 wm- 2 . A large body of research suggests that the IPCC has got it backwards, that it is the sun's influence that is responsible for the lion's share of climate change during the past century and beyond. • The total energy output of the sun changes by only 0.1 per cent during the course of the solar cycle, although larger changes may be possible over periods of centuries. On the other hand, the ultraviolet radiation from the sun can change by several per cent over the solar cycle - as indeed noted by observing changes in stratospheric 29