Tuesday, November 29, 2011

2011 hottest year globally with a La Niña event, 10th warmest on record

2011 is likely to be the world's tenth warmest year on record. This is despite a particularly strong La Niña which usually acts to dampen global temperatures, according to the World Meteorological Organisation (WMO). The WMO has released its summary and status of the global climate and weather for 2011 at the United Nations Framework Convention on Climate Change talks taking place in Durban South Africa.

"Concentrations of greenhouse gases in the atmosphere have reached new highs. They are very rapidly approaching levels consistent with a 2 to 2.4 degree Centigrade rise in average global temperatures which scientists believe could trigger far reaching and irreversible changes in our Earth, biosphere and oceans," said WMO Secretary-General Michel Jarraud.

The highest greenhouse gas emissions increase on record were recorded in 2010. The International Energy Agency has warned that a Bold change of direction needed globally to meet climate commitments. Scientists have modelled that Carbon Emissions need to peak this decade to meet 2 °C temperature goal that was made at the 2009 Copenhagen climate talks and confirmed at the 2010 Cancun talks.

"Our role is to provide the scientific knowledge to inform action by decision makers," said Michel Jarraud. “Our science is solid and it proves unequivocally that the world is warming and that this warming is due to human activities,”

La Niña dominated weather from the second half of 2010 and continued until May 2011. It was closely associated with many of the year’s notable regional climate events, including drought in east Africa, the central equatorial Pacific, the southern United States, and flooding in southern Africa, the Philipines, eastern Australia and southern Asia. According to the WMO strong La Niña years like 2010 are typically 0.10 to 0.15°C cooler than the years preceding and following them. 2011’s global temperatures followed this pattern, being lower than those of 2010, but were still warmer than the most recent moderate to strong La Niña years in 2008, 2000 and 1989.

A weak La Niña has again developed this year but is not expected to rival the 2010 La Niña in strength.

Global Temperature Anomolies

Surface temperatures over most land areas continue to be above the long term average. Northern Russia experienced high temperatures about 4°C above average in places from January to October. The 2011 Russian spring was especially warm with some stations more than 9°C above average for the season, with a hot summer. It was the third-hottest on record in Moscow, but below the extreme heatwave of 2010. Other Northern European countries experienced hot summer conditions with Helsinki in Finland having its hottest summer in nearly 200 years of data, and Armenia setting an all-time national record at 43.7°C. Much of Europe, southwest Asia and northern and central Africa, as well as the southern United States and northern Mexico, most of eastern Canada , and Greenland experienced 1°C or more above average from January to October 2011.

Below average temperature anomolies also occurred in northern and central Australia where temperatures were up to 1°C below average in places, due to above-average cloudiness and heavy rain early in the year. The western United States, south-western Canada, ,parts of east Asia, the Indochina Peninsula, eastern China and the Korean Peninsula also experienced below normal temperatures.

Arctic Sea Ice at near minimum

Arctic sea ice extent was the second lowest on record just behind 2007, with the minimum reached on 9th September, 2011, at 4.33 million square kilometres (35% below the 1979-2000 average). Both the Northwest and Northeast Passages were ice-free for periods during the 2011 summer. Sea ice volume was even further below average and was estimated at a new record low of 4200 cubic kilometres, surpassing the record of 4580 cubic kilometres set in 2010.

Reduced Tropical Cyclone activity

There was decreased tropical cyclone activity in 2011, although the incidence varies between ocean basins. The IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) reported that the average number of cyclones was likely to decrease slightly, but with a tendency for cyclones to develop with greater intensity due to increased wind speed. The most intense cyclone to make landfall during the year was Category 4 Tropical Cyclone Yasi which hit the Queensland coast between Townsville and Cairns devestating a substantial proportion of the banana crop but only resulting in one death due to the warnings and disaster risk management plans of the State Government.

There were many other Extreme weather events noted in the WMO statement including:

  • severe drought then flood in East Africa,
  • major floods in south-east Asia during the monsoon season which particularly affected Laos, Thailand, and the Mekong river basin.
  • major floods in Pakistan
  • record drought in Texas, with exceptionally hot summer temperatures : mean temperatures for June to August were 30.4°C (86.7°F), being 3.0°C (5.4°F) above the long-term average, and the highest ever recorded for any American state. The high temperatures and drought conditions exacerbated conditions for dust storms and severe wildfires.
  • Above normal rainfall and Severe flooding for the US midwest and Canada
  • Torrential rain and extreme flooding in Brazil which killed over 900 people
  • Drought in the central Pacific affecting the drinking supplies of Tuvalu and Tokelau which had to import drinking water.

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