Shock: Global Warming Still Happening!

Poneke is the local advocate for the view that global warming stopped in 1998. This canard is related to the fact that 1998 was just a shockingly hot year, the hottest on record.

It is true that warming in the last decade is slower than in the previous
decade due to a dramatic El Nino event in 1998 and La Nina conditions in the last twelve months or so.

However if you get the global average temperature data and fit a line to the last ten years then sure enough it has a positive gradient indicating a warming trend. For what that is worth on such a short timescale.

There is as yet no evidence that the underlying warming trend in global average temperatures has changed.

The Met Office in the UK has just released a press release to go along with this plot of their latest data (their methodology for this data is indeed described in a 2006 peer reviewed article.). (Hat-tip Climate Progress)

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.

But once again a picture is worth a thousand words. Here is a plot of global average temperatures (relative the the average temperature during 1961-1990) for the last thirty years or so.



It's really the thirty year trend that you should pay attention to, that is about the shortest period you should be looking at to determine long term trends related to climate rather than weather.

In their discussion of the current La Nina related "low" temperatures, they note

despite this temporary cooling, 2008 is still likely to be the seventh warmest on the global record.

As a result of such fluctuations, global average temperature trends calculated over ten-year periods have varied since the mid-1970s, from a modest cooling to a warming rate of more than 0.3 °C per decade. Similar behaviour is also seen in individual model predictions of future climate change where the long-term warming trend is forecast to exceed 2 °C per century. Even then, due to the natural variations in climate, we expect to see ten-year periods both globally and regionally with little or no warming and other ten-year periods with very rapid warming. This complex behaviour of the climate system shows why we need to examine much longer periods than ten years if we are to fully understand and quantify how the climate is changing.