Scientists at York and Ottawa universities are suggesting that the warming slowdown of the last few years may be incorrect. Their new study suggests that average continued global warming has continued at 0.12°C per decade, rather than the 0.05°C per decade as suggested by the Met Office, NASA and NOAA. This is in line with the IPCC’s long term trend, and shows that the global temperature rise of the past 15 years has been greatly underestimated.
It may also provide at least part of the explanation to the problem that the recent lack of warming on land cannot be explained by reductions in the total energy the Earth receives from the Sun. This has puzzled scientists and led to suggestions that the oceans may be absorbing more heat than previously.
The reason behind the discrepancy in perceived warming is twofold: gaps in the global weather stations, and differences in warming in different parts of the world. Gaps in the weather records would not matter if warming is uniform across the world. But the Arctic has warmed about twice as fast the global average in recent years – and it’s here, as well as in parts of Africa, where there are gaps in the observed climate data.
The researchers have developed a new method to fill in these data gaps. They have used satellite data not simply to fill the gaps of ground monitoring (satellites cannot measure ground temperature directly) but to assess the difference between satellite-recorded atmospheric measurements and those on the ground. The new method has been extensively validated with known data gaps between the two sets of measurements, and then applied to the Met Office’s otherwise state-of-the-art climate model.
And the results fit the expected long-term warming trend. The new IPCC report concludes that the warming over the last 15 years (1998–2012) has progressed at 0.05°C per decade), which is smaller than the rate of 0.12°C per decade calculated over the period 1951. The new method of filling the data gaps for the last 15 years produces a warming trend of 0.12 °C per decade - exactly the same as the IPCC’s long-term trend.
The corrected data (bold lines) are shown in the graph compared to the uncorrected ones (thin lines). The temperatures of the last three years have become a little warmer, the year 1998 a little cooler.
So it seems that the we may not have had a slowdown in the rate of warming in recent years, after all. Just the news to re-affirm the importance of making progress at the Warsaw climate talks this week and next, to redouble our own mitigation efforts, and to ensure that adaptation for the natural environment gets the attention and resources it needs.