Temperatures higher than ever, but rate slowed by pollution

Ahead of the latest UN talks on climate change in Mexico, the Met Office has released it analysis of long- and short-term trends in climate, revealing that the evidence for human-made warming has grown even stronger in the past year.
The Met Office says there is overwhelming evidence of warming in a wide range of climate indicators, not just surface temperature. In providing the evidence of continued warming and drawing from the work of more than 20 institutions worldwide, the Met Office Hadley Centre compiled results for a range of climate indicators. The multiple data sets used for each indicator are from diverse sources such as satellites, weather balloons, weather stations, ships, ocean buoys and field surveys.
The changes include: increases in water temperature at the sea surface down a depth of hundreds of meters; an increase in humidity as a warmer atmosphere holds more moisture; increases in sea level as warmer waters expand and land- ice melts; and shrinking of Arctic sea-ice, glaciers and Northern Hemisphere spring snow cover.

Since the late 1970s the long- term rate of surface warming has been about 0.16'C per decade. However, over the past decade the rate of warming has decreased. One of the major factors is pollution over Asia, where the huge growth in coal-fired power stations mean aerosols like sulphur are being pumped into the air. This reflects sunlight, cooling the land surface temperature.

Dr Vicky Pope, Head of Climate Change Advice, said pollution maybe causing a cooling effect. 'A possible increase in aerosol emissions from Asia in the last decade may have contributed substantially to the recent slowdown," she said. 'Aerosols cool the climate by reflecting the sunlight." Another factor that has reduced the rate of warming is a prolonged minimum in the solar cycle, meaning the Earth is receiving slightly less heat from the sun.