Global Warming Enthusiasts have held the floor for too long. It is time for genuine climate scientists to take the initiative and adopt, address, and promote the concept of Peak Warmth.
What exactly is Peak Warmth?
The well-known concept of Peak Oil is the point in time when the maximum rate of extraction of petroleum is reached. Peak Warmth is an unrelated but similar concept. Peak Warmth is that point when global temperatures inevitably reach their maximum before beginning to cool. Included in our discussion of the hiatus, pause, slowdown, or plateau in global temperatures, which may be followed by temperatures going up, down, or sideways, we need to consider Peak Warmth, as its consequences could be enormous.
The first thing to note of course is that Peak Warmth is well and truly past- in fact, around 5,000 to 8,000 years past. Many studies from around the world show the Holocene Optimum was from one to several degrees Celsius warmer than now, in different regions of the globe. The previous Eemian interglacial appears to have been even warmer. The Holocene has also had periods of millennial-scale variability in temperature and precipitation (think Mediaeval Warm Period, Little Ice Age). In various parts of the world, regional temperature change of four degrees Celsius in a century has not been unusual, so there’s nothing unprecedented about recent warming.
However, the focus of this post is the recent warming of the past 160 years.
Fig. 1: Hadcrut4 since 1850
Global Warming Enthusiasts can see no end to the recent warming, at least not without massive cuts to greenhouse gas emissions. They need to be pinned down: what will happen after 2100? Will there be runaway warming? Will temperatures continue to rise, and by how much?
Sceptics of the validity of the IPCC’s global warming scenarios have a different view. If the recent temperature increase is mainly due to natural causes, then a decrease at some stage is very likely. Some sceptics will say that natural influences will shortly cause (or have already caused) temperatures to begin cooling. Others (including myself) will say “We don’t know and can’t predict what will happen, or when”. We note, however, that going by the past, future cooling is inevitable- the instrumental record, such as it is, shows short warming phases are followed by cooling. The Dark Ages followed the Roman Warm Period, and the Little Ice Age followed the Mediaeval Warm Period. And while we don’t know the timing or mechanism of glacial inception which could be decades, centuries, or millennia away, we are overdue for the next glaciation.
Are there any indications of Peak Warmth? Arguably one of the best temperature datasets is that of the satellite derived UAH (University of Alabama- Huntsville). The Temperature of the Lower Troposphere gives a good indication of what the bulk of the atmosphere is doing. Unfortunately, we only have data since December 1978.
Fig. 2: UAH monthly temperature anomaly data for the Globe, December 1978 to May 2015. (The x-axis labels show December of each year.)
During the satellite era, the global temperature record shows 15 years of modest warming, then a rapid increase between the early 1990s and 2001 – 2002. (This period includes but is independent of the 1997-1998 Super El Nino.) The pause is undeniable since then- a bit over 13 years.
Actually, it is a small cooling.
Fig. 3: Phases of warming and cooling in UAH data
For the benefit of those who think including the Super El Nino exaggerates the trend of the rapid warming phase, excluding 1997, 1998, and 1999 gives a trend of +1.54C- just 0.07C less.
While we can say that current temperature trends are not consistent with IPCC projections, and alternative climate scenarios must be considered, it is too early to say whether we have reached or passed Peak Warmth of the current warm period, or if there will be future warming phases to a higher peak. We won’t know until many years afterwards. It is possible that Peak Warmth will be identified as occurring in a single month or year (for example, April 1998), but it is also possible that it will be seen as a period of some decades or even centuries.
I hope I am not around to see the cooling which will follow Peak Warmth. A long plateau at about current temperatures, or even a small decline, would not be detrimental for the world, but unlike Elsa, cold does bother me. While I have great faith in the ability of humankind to adapt to future challenges, another Little Ice Age would have very serious consequences for world food production, and the next glacial period must surely bring an end to civilization as we now know it.
It is time for genuine climate scientists to adopt and address the concept of Peak Warmth. The Precautionary Principle, invoked to justify measures to combat or mitigate global warming, needs to be invoked to address the consequences of future global cooling. Myopic denial of the pause wastes time and resources which must be better spent in studying little understood influences on climate such as clouds, rather than the current fixation on greenhouse gases as a cause of warming to the exclusion of all else.
We do indeed live in interesting times.