Tiscali Quicklinks. Please visit our Accessibility Page for a list of the Access Keys you can use to find your way around the site, skip directly to the main navigation, to the page content, or to more links within reference.
In 1988, the World Meteorological Organization (WMO) and the United Nations (UN) set up the Intergovernmental Panel on Climate Change (IPCC), a body of more than two thousand scientists, to investigate the causes of and issue predictions regarding climate change.
In 2007, the IPCC's Fourth Assessment Report stated that: most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increased in anthropogenic (human) greenhouse gas concentrations. The IPCC predicts that a doubling of carbon dioxide concentrations, expected before the end of the 21st century, would probably increase the average global temperature by 24.5°C/3.68.1°F.
Assessing the impact of humankind on the global climate is complicated by the natural variability on both geological and human time scales. The present episode of global warming has thus far still left England approximately 1°C/1.8°F cooler than during the peak of the so-called Medieval Warm Period from 1000 to 1400. The latter was part of a purely natural climatic fluctuation. The consensus view of climatologists is that the Medieval Warm Period was not on a global scale, but this is still a contentious topic.
In addition to a rise in average global temperature, global warming has caused seasonal variations to be more pronounced in recent decades. Examples are the most severe winter on record in the eastern USA 197677, and the record heat waves in the Netherlands and Denmark the following year. Mountain glaciers have shrunk, late summer Arctic sea-ice has thinned by 40%, and sea levels have risen by 1020 cm/48 in. Scientists have predicted a greater number of extreme weather events, and sea levels are expected to rise by 988 cm/435 in by 2100. 1998 was the warmest year globally of the last millennium, according to US researchers who used tree rings and ice cores to determine temperatures over the past 1,000 years.