My discussion will be centered on two ideas. First, although global temperatures have risen since the turn of the 20th century, the current temperature regime does not represent anything unusual compared to the past. Second, despite media reports to the contrary, catastrophically rising temperatures in the coming decades are not likely to occur.
Let’s start the discussion about how our climate has changed over the years. We know the earth has had periodic ice ages that lasted up to 100,000 years or more with warmer inter-glacial periods in between. Here’s a chart from the Utah Geological Survey showing the cycle over the past 450,000 years.
That last sharp increase on the right side of the chart shows the end of the most recent glacial period called the Wisconsin Glaciation in North America. The swings in temperature from the bottoms to the tops of the cycles average about 20 degrees Fahrenheit.
Here are a few observations. First, it looks like the glacial periods are getting longer. Second, the current inter-glacial is about eight degrees cooler currently than the maximum temperature of the one preceding it. And finally, if we take closer look at the current inter-glacial, what do we see?
About five to ten thousand years ago it was about two degrees warmer than it is now. That period is known as the Holocene Climatic Optimum.
Now let’s take a closer look at the last 10,000 years. Here’s a chart presented in 2013 by ARD, Germany’s version of the BBC or our own PBS:
In this chart we see actually two Holocene Optima occurred between four thousand and eight thousand years ago. After the Holocene Optima there are cyclical fluctuations of warmer and cooler periods – including the Roman Warm Period, Medieval Warm Period, the Little Ice Age and the current warming period that began around 1850.
Now there’s no question the earth has warmed since 1850, but that was after the Little Ice Age, so I think the warming was welcome. And from the ARD chart, it is clear that there were three comparably warm periods before our current warming period, and that the current warming period is dwarfed by the two Holocene temperature peaks.
In sum, I argue there is persuasive evidence that the current temperature regime is not unusual compared to historical norms. This is a good start but we need more information to inform policy decisions regarding climate change.
What about the warming since the turn of the 20th century? Let’s look at some passages from Meteorology Today. This textbook provides a wonderful perspective on the evolution of climatology because the first edition was published in 1982 and the most recent 13th Edition came out at the beginning of this year. This quote is from the Sixth Edition, published in 2000:
Indeed, because the interactions between the earth and its atmosphere are so complex, it is difficult to unequivocally prove that the recent warming trend has been due primarily to increasing concentrations of greenhouse gases. The problem is that any human-induced signal of climate change is superimposed on a background of natural climatic variations (“noise”) such as the El Niño-Southern oscillation (ENSO) phenomenon. Moreover, in the temperature observations it is difficult to separate a signal from the noise of natural climate variability.
Notice the moderate stance with respect to the recent warming. Notice that the
authors of this text are not saying “The science is settled.” Far from it. Things change as the Seventh Edition was published in 2003. In the chapter on climate change the authors include the famous hockey stick chart, which turned the Medieval Warm Period and Little Ice Age into one long decline, followed by record high temperatures not seen in a thousand years:
This chart, which also appeared in the Third Annual Report from the Intergovernmental Panel on Climate Change, became very controversial. Indeed, in February 2005, an article published in Geophysical Research Letters, published by the American Geophysical Union, concluded the following:
However, it has not been previously noted in print that, prior to their principal components (PCs) analysis on tree ring networks, they carried out an unusual data transformation which strongly affects the resulting PCs.
Their method, when tested on persistent red noise, nearly always produces a hockey stick shaped first principal component (PC1) and overstates the first eigenvalue.
Pretty cool, right? Put in nearly random data and no matter what, it gets transformed into a hockey stick.
I am going to circle back to the Seventh Edition of Meteorology Today, the one that came out in 2003. The authors talk about many possible reasons why climate might change, like feedback mechanisms, plate tectonics, the earth’s orbit, aerosols in the atmosphere, volcanic eruptions, and variations in solar output.
They also wonder why the climate began to cool after 1940 and what caused the “exceptionally cold winters during the 14th and 19th centuries.” They also continue as they did in previous editions:
… it is important to realize that the interactions between the earth and its atmosphere are so complex that it is difficult to unequivocally prove that the warming trend during the past 100 years has been due primarily to increasing concentrations of greenhouses gases. The problem is that any human-induced signal of climate change is superimposed on a background of natural climatic variations (“noise”), such as the El Niño-Southern Oscillation (ENSO) phenomenon. Moreover, in the temperature observations, it is difficult to separate a signal from the noise of natural climate variability.
However, today’s more sophisticated climate models are much better at filtering out this noise while at the same time taking into account those forcing agents that are both natural and human-induced.
It seems like the authors want to have it both ways. In the end, however, they defer to the climate models with a quote from the third IPCC report:
In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the past 50 years is likely to have been due to the increase in greenhouse gas concentrations.
Just so you know, in the jargon of the IPCC, “likely” means greater than a 66% chance.
How can non-scientists evaluate the “complex climate models?” One way is to compare their projections to actual results. According to the Seventh Edition of Meteorology Today published in 2003, climate models were projecting temperature increases between 1.4°C and 5.8°C from 1990 to the year 2100. As it turns out, the actual global temperature rate of change through mid-2021 was slightly below the lower end of projected range.
Here’s another chart of data from NOAA that suggests the rate of change in temperature in the United States has been close to zero during the time since the 2003 edition of Meteorology Today was published:
So, what we see is little to no temperature increase in the United States over the past fifteen years, which is consistent with other unbiased regional temperature data. Moreover, the lack of a rising trend is probably not just happenstance.
Here’s an interesting chart:
Do you recall that we talked about climate models projecting global temperature increases between 1.4°C and 5.8°C in the 2003 edition of Meteorology Today?
Well, published estimates of the effect of increasing concentrations of carbon dioxide have declined since then.
So, what’s a policy maker to do? Since global temperature sensitivity estimates for increasing concentrations of carbon dioxide have come down sharply in the past 15 years, and at the same time, considering that global temperatures have likely not changed substantially, and finally, since the current temperature regime
is not unusual compared to past regimes, I would argue that extreme responses to any perceived threat from our changing climate are not justifiable.
Policies proposed by the catastrophic global warming crowd will cost the United States jobs. Their solutions will not change our climate meaningfully. In short, if we follow their lead, we will be poorer, and the lower economic output will hurt the most vulnerable amongst us.
We don’t have to put people out of work in Pennsylvania, West Virginia and South
Dakota. We don’t have to curtail energy exploration in Alaska or cancel new pipelines. The reckless push towards “net-zero emissions” will only make us poorer and less secure.
What we should do is encourage research and development in the energy industry. We should continue our research in clean coal, and in cleaner ways to burn oil and natural gas. We should invest in nuclear energy, and in hydrogen as an energy source. And, yes, we should continue our research into renewables. If someone can solve the intermittency problem – that is, come up with a clean and efficient way to store energy – renewable energy like solar and wind will become much more valuable to us.
In sum, encouraging the energy industry to innovate will lead to a prosperous, clean and secure environment not only for us here in the United States but also for the world as a whole.