Guest Post by Bob Tisdale
The UKMO issued their most recent 5-year global temperature forecast about a week ago. See their Decadal forecast press release for 2015. It has been getting a little press recently. The forecast description wasn’t as clear as it could have been, but the UKMO openly displayed the failure of the forecast from 2009 sea surface temperatures.
The summary includes three bullet points. The first reads:
Averaged over the five-year period 2015-2019, forecast patterns suggest enhanced warming over land, and at high northern latitudes. There is some indication of continued cool conditions in the Southern Ocean, and of a developing cooling in the North Atlantic sub-polar gyre. The latter is potentially important for climate impacts over Europe, America and Africa.
This suggests that the UKMO’s models are capable of regional forecasting, yet at the end of the forecast they openly discuss factors that prevent this.
The second bullet point is:
Averaged over the five-year period 2015-2019, global average temperature is expected to remain high and is likely to be between 0.18°C and 0.46°C above the long-term (1981-2010) average of 14.3°C. This compares with an anomaly of +0.26°C observed in 2010 and 2014, currently the warmest years on record.
In other words, over the next five years, their models forecast that global surfaces may be a little warmer or a little cooler than 2014, as much as 0.2 deg C warmer or as much as 0.08 deg C cooler. [Sarc on.] That narrows it down. [Sarc off.]
Also, that second bullet point is basically the same as the 5-year forecast from 2014. See the WaybackMachine archive here:
Averaged over the five-year period 2014-2018, global average temperature is expected to remain high and is likely to be between 0.17°C and 0.43°C above the long-term (1981-2010) average. This compares with an anomaly of +0.26°C observed in 2010, the warmest year on record.
The final bullet point from the 2015 forecast reads:
Although the forecast generally indicates that global temperatures will remain high, it is not yet possible to predict exactly when the slowdown in surface warming will end.
The phrase “global temperatures will remain high” is curious. It leads one to believe that global surface temperatures might somehow return to “normal”.
Also, remarkably, the UKMO acknowledged in that bullet point (1) that the “slowdown in surface warming” continues and (2) that they still have no idea when the “slowdown” will end.
I suspect in response to that “slowdown in surface warming” statement we might see some flawed arguments that global warming continues, along with some graphs that show long-term (1900 to 2014) and short-term (1998-2014) trends are comparable. See my Figure 1. Similar graphs have appeared around the blogosphere.
My Figure 1
Why is that a flawed argument?
Predictions of gloom and doom are not based on warming rates of 0.06 to 0.08 deg C/decade. The climate models used by the IPCC for their recent 5th Assessment Report simulate much higher warming rates for the short-term. That is, the recent CMIP5 model estimates of short-term (1998-2014) warming and the projections of future global warming initially align with the warming rate from 1975 to present, not from 1900 to present. See the two graphs in my Figure 2.
My Figure 2
THE FORECAST FROM 2009 GLOBAL SEA SURFACE TEMPERATURES WAS A CATASTROPHIC FAILURE
Under the heading of Verification, the second paragraph of the 2015 UKMO 5-year forecast reads and includes the following illustration:
The maps in Figure 4 compare observed (A) and forecast (B) surface temperatures (°C) for November 2009 to October 2014 relative to the 1981-2010 long-term average. Forecasts were made starting from November 2009 using the latest system based on HadGEM3. Stippling shows regions where the observed temperatures do not lie within the 5-95% range of the forecast.
Their Figure 4
Just in case you’re having difficulty seeing the differences and the stippling, see Animation 1. I’ve darkened the illustrations to bring out the stippling, which covers most of the globe. That means for much of Earth’s surface the observed global surface temperatures were outside the range of the multiple climate model runs used in the forecast. In other words, the 2009-based forecast was an abysmal failure.
The closing paragraph begins:
The decadal forecast system predicted enhanced warming over high northern latitudes, and cooling in the Southern Ocean and North Atlantic sub-polar gyre. These are in broad agreement with the observations, although there are differences in the precise magnitude and location of anomalies.
“Broad agreement” is an odd phrase to use when stippling indicates the observed temperatures in much of the Southern Ocean and in the high latitudes of the North Atlantic did “not lie within the 5-95% range of the forecast”.
UKMO goes on to explain why the models failed in other regions:
However, the forecast did not predict the cooling in the eastern tropical Pacific associated with the negative phase of the Pacific Decadal Oscillation (PDO), and the cooling over parts of China associated with a negative Arctic Oscillation (AO). This is consistent with the fact that decadal prediction systems are not yet capable of predicting the PDO or the AO for the coming five years.
And the fact that the decadal prediction systems are still not able to predict the Arctic Oscillation and the Pacific Decadal Oscillation (an aftereffect primarily of El Niño and La Niña events) highlights a couple of cold realities: 5-year forecasts from the past that are more successful are based solely on luck, not skill, and all future regional forecasts are basically valueless until the UKMO is capable of forecasting natural variability such as El Niño and La Niña events, the Pacific Decadal Oscillation, the Arctic Oscillation, the North Atlantic Oscillation, etc.