Saturday, February 13, 2010

Climate change fact of the week: Where in the world have temperatures warmed?

Q: Where has it warmed?

A: Everywhere

Explanation of figure 1: Long term temperature trend of each region of the globe between 1970 and 2009 (created at NASA GISTEMP). Scale at bottom shows what temperature change (in dC) each colour represents. Ie: Areas that have cooled are shown in blue, areas that have warmed range from yellow to orange to red, with red representing the most warming. Areas which no change are in white. Grey represents areas with a lack of data.

  • Warming has been recorded over the entire globe since 1970, ie: global warming.
  • The long term temperature trend from 1970 to 2009 shows warming of 0.67 dC (nb: this is not a comparison of 1970 with 2009 but the trend in worldwide temperatures over the whole 40 year period).
  • Warming has been greatest in high northern latitudes (around the north pole), consistent with what is predicted in a warming world.
  • The only area without consistent warming is in and around parts of Antarctica, scientists think this may be due to the hole in the ozone layer*.

+/- Further info (click to expand)

While the earth is warming, it is important to remember that not every part of the world will show record or near record warmth every year. This is due to natural variation. For example, figure 2 shows the worldwide temperature anomaly in 2009. Globally 2009 was the second equal warmest year on record, however during 2009 temperatures in parts of the USA and Canada were near the 1950-1980 average (coloured white). This is regional natural variation (ie: weather not climate) and is why looking at long term trends (figure 1) is the best way to understand how the climate is changing.

Explanation of figure 2: Worldwide temperature in each part of the world in 2009 compared to the 1950-1981 temperature average. 2009 was tied for the second warmest year in the instrumental record. Figure from NASA GISTEMP.

*The lack of warming over parts of Antarctica is an active area of research for scientists. It appears to be due to a strengthening of winds that circle Antarctica known as SAM which has been caused in turn by cooling in the high atmosphere due to the ozone hole. This is a complex topic but if you are really keen see the IPCC 2007 report WG1 chapter 3, or scientific articles here and here.

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