On Warming Holes (Global Warming Gaps)


Animation showing the 25-year and 40-year trends in surface air temperature in the Cowtan and Way v2.0 dataset, with plots to the right showing the fraction of the earth surface in a cooling trend (the blue areas in maps).

Ed Hawkins at his blog provides above the display of variability of warming and cooling across the globe. The post is entitled Regional Temperatures This Century (here).

We found that some regions experience periods of cooling at this timeframe even when global temperature is increasing rapidly. Cooling periods of 25 years duration occurred in 13 to 74 % of the earth surface through the observed record, and cooling periods of 40 years occurred in 6 to 71% of the earth surface, including in the most recent decades. Cooling periods are more prevalent where the long-term trend is low such as in the Southern Ocean, and/or where decadal variability is high such as Pacific Ocean regions influenced by the Inter-Decadal Pacific Oscillation (IPO). However, there are cases where low trend or high variability due to the IPO (or Atlantic Multi-decadal Oscillation) are not the only factors, and there may be a role for forcings and other regional effects. These cases include the well-known ‘warming hole’ in the south east US through the last half of the 20th Century (noting this ‘hole’ has an important seasonal aspect to it) and the recent cooling in northern Australia linked to increasing cloud and rainfall.

He refers to the cooling regions as “warming holes”. Since there are periods where cooling dominates globally, we could also refer to exceptional regions as “warm spots.” This shows dynamically how regional climate trends differ over time. For example, over the last century in the continental US, about a third of land stations showed cooling trends contrary to the slightly warming average overall.

Cautionary note regarding the Cowtan and Way 2.0 Dataset

This dataset is controversial in its use of “krieging” to spread temperature readings from a handful of land stations across the full extent of the Arctic (and Antarctic) including surfaces of ocean, ice and mixtures of the two. As the charts show, this results in extra warming in the Arctic, double the trend shown by UAH (satellite) dataset.

Another example of the inconsistency of “global warming” is provided by NOAA’s presentation of continental temperatures. (here) The table below is for October 2016, and shows not only variability, but also how land temperatures are falling following El Nino’s disappearance.

CONTINENT ANOMALY (1910-2000) TREND (1910-2016) RANK
°C °F °C °F YEAR(S) °C °F
North America +1.33 +2.39 +0.05 +0.09 Warmest 7ᵗʰ 1963 +2.16 +3.89
Coolest 101ˢᵗ 1919 -1.94 -3.49
South America +0.85 +1.53 +0.17 +0.30 Warmest 15ᵗʰ 2014 +1.60 +2.88
Coolest 92ⁿᵈ 1922 -1.04 -1.87
Ties: 1994
Europe +0.40 +0.72 +0.11 +0.20 Warmest 41ˢᵗ 2006, 2001 +1.96 +3.53
Coolest 67ᵗʰ 1912 -1.99 -3.58
Africa +1.35 +2.43 +0.09 +0.16 Warmest 2ⁿᵈ 2015 +1.59 +2.86
Coolest 106ᵗʰ 1910 -0.65 -1.17
Asia -0.15 -0.27 +0.10 +0.18 Warmest 69ᵗʰ 2011 +1.76 +3.17
Coolest 39ᵗʰ 1912 -2.22 -4.00
Oceania +0.21 +0.38 +0.13 +0.23 Warmest 44ᵗʰ 2015 +2.71 +4.88
Coolest 64ᵗʰ 1910 -1.15 -2.07


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