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Global TemperatureThere is no single thermometer measuring the global temperature. Instead, individual thermometer measurements taken every day at several thousand stations over the land areas of the world are combined with thousands more measurements of sea surface temperature taken from ships moving over the oceans to produce an estimate of global average temperature every month (see the sections on how climate is measured ). From these records, eleven of the last twelve years (1995–2006) rank among the 12 warmest years in the instrumental record of global temperature (since 1850). The total global temperature increase from the 1850s throught to 2005 is 0.76°C (1.36°F) and the rate of warming averaged over the last 50 years is nearly twice that for the last 100 years. An increasing rate of warming has taken place over the last 25 years, and 11 of the 12 warmest years on record have occurred in the past 12 years. Above the surface, global observations since the late 1950s show that the troposphere (up to about 10 km) has warmed at a slightly greater rate than the surface, while the stratosphere (about 10–30 km) has cooled markedly since 1979. This is in accord with physical expectations and most model results. Confirmation of a global temperature rise comes from the observed temperature increases in the oceans, observations of sea level rise, glacial melt, sea ice retreat in the Arctic and diminished snow cover in the Northern Hemisphere. Global average temperature is forecast to rise 4°C (7.2°F) toward the end of the 21st century, and this is a mere 90 years away! Even if began today, and stopped most of our greenhouse gas emissions overnight, we would still see a temperature rise of around 2°C (3.6°F) by 2090-2100. David Spratt and Philip Sutton explain in their paper Code Red what will happen with three degrees of warming, and how dangerous this is. This rapid rise in temperature is unmatched in the last million years, and even then, the data indicate that the global warming at the end of an
ice age
was a gradual process taking about 5,000 years. Our human (
anthropogenic
) actions have ramped up the rate of change not evidenced in any record, and we are leaving ourselves very little time to
adapt.
The 4th IPCC Report also states that, "analysis of long-term changes in daily temperature extremes has recently become possible for many regions of the world (parts of North America and southern South America, Europe, northern and eastern Asia, southern Africa and Australasia). Especially since the 1950s, these records show a decrease in the number of very cold days and nights and an increase in the number of extremely hot days and warm nights. The length of the frost-free season has increased in most mid- and high-latitude regions of both hemispheres. In the Northern Hemisphere, this is mostly manifest as an earlier start to spring."
Regional Temperature Anomalies The beginning of 2006 was unusually mild in large parts of North America and the western European Arctic islands, though there were harsh winter conditions in Asia, the Russian Federation and parts of Eastern Europe. Canada experienced its mildest winter and spring on record, the USA its warmest January-September on record and the monthly temperatures in the Arctic island of Spitsbergen (Svalbard Lufthavn) for January and April included new highs with anomalies of +12.6°C and +12.2°C, respectively. Persistent extreme heat affected much of eastern Australia from late December 2005 until early March with many records being set (e.g. second hottest day on record in Sydney with 44.2°C/111.6°F on 1 January). Spring 2006 (September-November) was Australia’s warmest since seasonal records were first compiled in 1950. Heat waves were also registered in Brazil from January until March 2006 (e.g. 44.6°C/112.3°F in Bom Jesus on 31 January – one of the highest temperatures ever recorded in Brazil). Several parts of Europe and the USA experienced heat waves with record temperatures in July and August of 2006. Air temperatures in many parts of the USA reached 40°C/104°F or more. The July European-average land-surface air temperature was the warmest on record at 2.7°C above the climatological normal. Autumn 2006 (September-November) was exceptional in large parts of Europe at more than 3°C warmer than the climatological normal from the north side of the Alps to southern Norway. In many countries it was the warmest autumn since official measurements began: records in central England go back to 1659 (1706 in The Netherlands and 1768 in Denmark).
Summary Based on science from the IPCC 4th Report, and consistent with observed increases in global temperature, there have been: - decreases in the length of river and lake ice seasons. - worldwide reduction in glacial mass and extent in the 20th century. - melting of the Greenland Ice Sheet has recently become apparent. - snow cover has decreased in many Northern Hemisphere regions. - sea ice thickness and extent have decreased in the Arctic in all seasons. - the oceans are warming - sea level is rising due to thermal expansion of the oceans and melting of land ice.
The
rapid rise in global temperature is
unmatched in the last million years. Normally, and when the Earth has
warmed
after an ice age, it is a gradual process taking about 5,000 years.
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