U.K. Ministry of Defence: Global warming goes on, deniers are deluded 2

The U.K.'s Met Office issued a blunt statement on Tuesday, "Global warming goes on," that begins:

Anyone who thinks global warming has stopped has their head in the sand. The evidence is clear -- the long-term trend in global temperatures is rising, and humans are largely responsible for this rise. Global warming does not mean that each year will be warmer than the last, natural phenomena will mean that some years will be much warmer and others cooler. You only need to look at 1998 to see a record-breaking warm year caused by a very strong El Niño. In the last couple of years, the underlying warming is partially masked caused by a strong La Niña. Despite this, 11 of the last 13 years are the warmest ever recorded.

Strong stuff from the U.K.'s official provider of climate and weather-related analysis, which is actually within the U.K.'s Ministry of Defence. The U.K.'s Guardian reported the story as "Met Office says climate change deniers deluded."

The Met Office has put together an interesting figure to show that global warming has continued at a pace of 0.17°C per decade since 1975 (red line), although the decadal trends (blue lines) have fluctuated wildly.

As the Met Office explains:

Average global temperatures are now some 0.75 °C warmer than they were 100 years ago. Since the mid-1970s, the increase in temperature has averaged more than 0.15 °C per decade. This rate of change is very unusual in the context of past changes and much more rapid than the warming at the end of the last ice age. Sea-surface temperatures have warmed slightly less than the global average whilst temperatures over land have warmed at a faster rate of almost 0.3 °C per decade.

Over the last ten years, global temperatures have warmed more slowly than the long-term trend. But this does not mean that global warming has slowed down or even stopped. It is entirely consistent with our understanding of natural fluctuations of the climate within a trend of continued long-term warming.

These natural fluctuations include the El Niño Southern Oscillations (ENSO) in the Pacific Ocean. In El Niño years -- those when cold surface water is not apparent in the tropical eastern Pacific -- global temperature is considerably warmer than normal. A particularly strong El Niño occurred in 1998 resulting in the warmest year on record across the globe. In La Niña years -- when cold water rises to the surface of the Pacific Ocean -- temperatures can be considerably colder than normal. Volcanic eruptions can also cause temporary drops in global temperatures because of huge amounts of dust thrown high into the atmosphere that reduce the amount of sunlight that reaches the surface. A La Nina was present throughout 2007 and much of 2008; -- despite this temporary cooling, 2008 is still likely to be the seventh warmest on the global record.

... current warming is being caused mainly by human emissions of greenhouse gases which have accumulated in the atmosphere and intensified the greenhouse effect by absorbing more of the thermal radiation emitted by the land and ocean. The Intergovernmental Panel on Climate Change concluded in its most recent assessment in 2007 that increases in man-made greenhouse gas concentrations have 'very likely' caused most of the overall increase in global average temperatures since the mid 20th century.

The brochure version is available here [PDF].

Double kudos to the Met Office for explaining this so clearly and for calling out the deniers.

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.

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