The meteorologists’ conclusions about global weather in the decade 2001-2010 were published yesterday, and they make uncomfortable reading: the 2000s was the warmest decade since modern measurements began in 1850, and the world experienced “unprecedented high-impact climate extremes”.
A report from the World Meteorological Organisation (WMO) showed that the global average temperature in 2001-2010 was 14.47°C – that is, 0.21°C hotter than in 1991-2000. Every year of the 2000s, except 2008, was among the ten warmest years on record.
The WMO’s report demolishes claims by climate science deniers that scientists’ main conclusions about the dangers of global warming are put in question by the slower-than-expected pace of year-by-year temperature increases in 2001-2010.
Kevin Anderson of the Tyndall Centre for Climate Change Research, in an interview on this web site (conducted before the WMO research was published) rebutted those claims – and the WMO report is striking for the way that it underlines (with triple, thick red lines) Anderson’s points that:
■ Average temperature rises were slower than in the 1990s, but the trend is unchanged. “Natural climate variability, caused in part by interactions between our atmosphere and oceans – as evidenced by El Nino and La Nina events – means that some years are cooler than others”, WMO Secretary General Michel Jarraud said. “On an annual basis, the global temperature curve is not a smooth one. On a long-term basis the underlying trend is clearly an upward direction, more so in recent times.”
■ To measure climate change, year-by-year changes are potentially misleading and longer periods need to be considered. “A decade is the minimum possible time frame for meaningful assessments of climate change”, Jarraud said. The WMO report showed that global warming was “significant” from 1971 to 2010 and that “the decadal rate of increase between 1991-2000 and 2001-2010 was unprecedented”.
The 2000s was warmest for both northern and southern hemispheres, and on land and at sea. The decline in Arctic sea ice accelerated and global mean sea levels rose by about 3 millimetres per year – almost twice the pace at which they rose during the 20th century.
The 2000s was also the second wettest decade since the start of the 20th century, and 2010 was the wettest year since records began. Tropical cyclone activity in the North Atlantic basin was at its highest level since 1855.
For us non-scientists who are trying to make sense of the issues, the conclusion is surely that we need to look at the all-round picture. Beware of isolated pieces of information that are often emphasised by climate science deniers, with the aim of deliberate obfuscation. (I wrote about their initial reaction to temperature information for the 2000s here.)