Back to Basics Part 1 – What is Global Warming?

Guest Post by Bob Tisdale

This is the first part of a two-part series of posts that present chapters from my recently published ebook On Global Warming and the Illusion of Control – Part 1.  The introductory post for the book is here (WattsUpWithThat cross post is here), and the book in pdf format is here (25 MB). Yes, the book is free.

The topic of this post is What is Global Warming?  The second post, to be published next week, is What is Climate Change?

1.2 – What is Global Warming?

The term “global warming” has come to mean the warming of our planet Earth (the surface, the lower atmosphere, and the oceans to depth) that has been caused by, and will be further enhanced by, the emissions of man-made greenhouse gases.  No one bothers calling it man-made global warming or anthropogenic global warming or human-induced global warming anymore.  Whenever a news report or article uses the term global warming, everyone now assumes they’re talking about the hypothetical man-made kind of warming.

There are many possible reasons why global warming has occurred over the past few decades, some of which are natural, but the primary focus of research has been on the consequences of increased emissions of carbon dioxide into the atmosphere that result from the burning of fossil fuels.

Graphs that show global land plus ocean surfaces warming since pre-industrial times are commonplace. Figure 1.2-1 shows the annual global land+ocean surface temperature anomalies, based on the UKMO HadCRUT4 reconstruction, from its start year in 1850 1880 through to 2014.  Based on the linear trend, global surfaces are warming at a not-very-alarming long-term rate of about 0.06 deg C/decade (about 0.10 deg F/ decade)…for a total warming of less than 0.8 deg C (about 1.4 deg F) since 1880.

The linear trend line also helps to illustrate that the warming was not continuous. Initially, there is a period of cooling followed by a period of warming until the mid-1940s. Then the cycle repeats itself with a period of cooling until the mid-1970s, followed by a warming period.  Because the rates of warming during the two warming periods are greater than the cooling rates during the two cooling periods, there is a positive warming trend.

That leaves us with a very basic question. Should we expect another multidecadal cooling period, or at least a slowdown lasting for a couple of decades, before another warming period?  Rephrased, would we expect the multidecadal (approximately 60-year) cycle to repeat itself?

Many persons believe the cycle will repeat into the future.  The climate modelers do not. Their models have been tuned to extend (and amplify) the warming from the more recent higher-than-average warming period out into the future, without accounting for the cyclical nature of global warming.  If the cycle continues into the future, then the climate models have simulated too much warming…way too much warming.

THE RATE OF WARMING IS SO SMALL WE HAVE TO BE TOLD GLOBAL WARMING IS HAPPENING.  WE CAN’T SENSE IT.

In the Introduction, I noted we have to be told global warming is occurring…that we as individuals would not be able to sense that global surface temperatures have warmed. Daily and seasonal variations in local temperatures are so great that we’d never notice the slight change in global surface temperatures we’ve experienced since the mid-1970s. It’s only about 0.7 deg C or 1.3 deg F (based on the linear trend), and it’s occurred over a 40-year period.

Think about how great the temperature variations are at your home: over the course of every year…and daily.  Here are examples from a widely referenced dataset.

In the two graphs in Figure 1.2-2, the increase in annual global surface temperature (red curves) since 1880 (same red curve as in Figure 1.2-1) is compared to daily maximums (orange curves) and minimums (dark green curves) for the Central England Temperature dataset, during that same timeframe. The top graph shows the three datasets in deg C, while the bottom graph shows them in deg F.

The UKMO Central England Temperature (a.k.a. HadCET or simply CET) dataset is the longest continuous temperature record in the world.  It is supported by the 1992 Parker et al. paper A new daily Central England Temperature series. As its name suggests, it is not based on a temperature record at one specific location but rather a group of locations in Central England.

Daily Central England maximum (Tmax) and minimum (Tmin) temperature data are available from the KNMI Climate Explorer, specifically the Daily climate indices webpage, starting in 1878.

The minimums of the green curves in Figure 1.2-2 above show the lowest temperatures reached each year, and the maximums are the highest annual temperatures.  Obviously, the range in temperatures that Central England sees every year dwarfs the rise in global surface temperatures.

Now let’s consider the daily change in temperature, from minimum to maximum.

Using the Central England Temperature data again for example, we can determine what climate scientists call the diurnal temperature range by subtracting the daily minimum temperatures from the daily maximums.  See Figure 1.2-3.  The global surface temperature anomalies are also included as a reference. As shown, there can be very large swings in daily temperatures.

As I wrote earlier, because the daily and seasonal variations in temperature where we live are so great, it’s very unlikely that we would be able to sense that global surface temperatures have warmed. We have to be told.  I suspect that’s why most people around the world rank global warming low on their list of priorities.  See the MyWorld2015.org poll The United Nations Global Survey for a Better World.

Some readers may recall a similar presentation by Dr. Richard Lindzen, Alfred P. Sloan Professor of Meteorology (emeritus) at the Massachusetts Institute of Technology, in one of his many lectures on global warming.  Yes, the idea for this topic came from his November 17, 2009 talk at Oberlin College.  See the YouTube video here. It’s a wonderful lecture.

BE WARY HOW THE TERM GLOBAL WARMING IS BEING USED

Global warming can mean different things to different people.  As a result, we have to be careful about how the term is used.  Let’s assume a reporter is interviewing a climate scientist…but unknown to the reporter, the scientist is a skeptic.

If the reporter were to ask: Do you believe in global warming?

And if the scientist answered:  Yes.  Numerous datasets indicate the Earth has warmed since the start of the 20^th Century.

That answer makes the scientist part of the consensus, the groupthink.

And if the reporter were to ask: Do you believe that mankind has contributed to global warming?

Scientist’s answer: Yes. Mankind has contributed to global warming in many ways.

The scientist didn’t specify what those “many ways” were. If the reporter was to stop there, the scientist would be thought to be a part of the groupthink.

But if the reporter asked: Do you believe that mankind is the primary cause of global warming and that future warming will lead to catastrophe?

Suppose now the scientist were to answer: Based on my research and detailed understanding of the data, climate models and their uncertainties, my answer is no.

For that answer, the scientist would likely be branded a heretic.

Different interpretations of the term global warming can also lead to questionable results in polls.

Bottom line:  Always be wary of term global warming and how it is being used.  Is the author discussing the fact that the surface of the Earth has warmed?  Is he or she discussing naturally caused warming or human-induced global warming?

ACCORDING TO A WELL-KNOWN AND WELL-RESPECTED CLIMATE SCIENTIST, “…NO PARTICULAR ABSOLUTE GLOBAL TEMPERATURE PROVIDES A RISK TO SOCIETY…” 

Every now and then, during the discussion of a global warming-related topic, a climate scientist—a member of the consensus—will make an amazing statement…or two.  Examples can be found in a blog post by Dr. Gavin Schmidt, Director of the Goddard Institute of Space Studies.  Dr. Schmidt wrote the following in his December 2014 blog post Absolute temperatures and relative anomalies, at RealClimate. (Blog post archived here.)  Dr. Schmidt was attempting to downplay the fact that there is a large range (about 3 deg C or about 5.4 deg F) in the absolute global surface temperatures produced by the climate models stored in the CMIP5 archive, which is roughly 3 times the warming we’ve experienced since pre-industrial times.  Dr. Schmidt states, where GMT is global mean temperature (my boldface and my brackets):

Most scientific discussions implicitly assume that these differences [in modeled absolute global surface temperatures] aren’t important i.e. the changes in temperature are robust to errors in the base GMT value, which is true, and perhaps more importantly, are focussed on the change of temperature anyway, since that is what impacts will be tied to. To be clear, no particular absolute global temperature provides a risk to society, it is the change in temperature compared to what we’ve been used to that matters.

See, I told you. That paragraph includes two memorable statements.

First: “…it is the change in temperature compared to what we’ve been used to that matters”.

Well, we’re “used to” wide variations in surface temperature every day, and “used to” even greater changes each year.

Second: “To be clear, no particular absolute global temperature provides a risk to society…”

I would hazard a guess that many of you are now wondering why politicians around the globe are concerned about global warming. If the absolute global mean temperature today provides no “risk to society”, and if an absolute global mean temperature that’s 2.0 to 4.0 deg C (3.6 to 7.2 deg F) higher than today provides no “risk to society”, then what’s all the hubbub about?  Based on Dr. Schmidt’s statement, should the priority then be adaptation to weather and rising sea levels, not reductions in greenhouse gas emissions?