So What Was The Perfect Pre-Industrial Global Temperature?

According to the Climate Change Alarmism crowd the earth was once perfect in every way, then we started to use fossil fuels. We don’t have enough actual temperature measurements from back then so to find out what it was like in 1850 you can use the climate models to “hindcast” the temperatures. Yes, those same models that failed to forecast the 20 year pause.

And here we are spending trillions of dollars to fight a problem we can’t actually measure or define.

From “Watts Up With That”

What Was Earth’s Preindustrial Global Mean Surface Temperature, In Absolute Terms Not Anomalies, Supposed to Be?

And What Have the Average Temperatures of Earth’s Surfaces Been Recently in Absolute Terms, Not Anomalies?

The answers may surprise you.

THIS POST HAS BEEN UPDATED. The update is near the end of the post.

Recently, the Intergovernmental Panel on Climate Change (IPCC) and the U.S. Global Change Research Program (USGCRP) have cranked up their alarmist propaganda, with the IPCC now pushing the goal of limiting global warming to 1.5 deg C above preindustrial global surface temperatures.

That, of course, initiates the title question, What Was Earth’s Preindustrial Global Mean Surface Temperature, In Absolute Terms Not Anomalies, Supposed to Be?

Four years ago, in the post On the Elusive Absolute Global Mean Surface Temperature – A Model-Data Comparison (WattsUpWithThat cross post is here), we illustrated and discussed the wide (3-deg C) span in the climate model simulations of global surface temperatures on an absolute, not anomaly, basis. Figure 1 below is Figure 5 from that post. In that post, we started the graphs in the year 1880 because the GISS Land-Ocean Temperature Index (LOTI) and NOAA NCDC (now NOAA NCEI) data started that year.

Figure 1

However, the spreadsheets I prepared for that post had the climate model hindcast outputs as far back as their common start year of 1861. (I say common start year of 1861 because the outputs of some models stored in the CMIP5 archive start in 1850 while others begin in 1861.) So I couldn’t use the climate model outputs stored on that spreadsheet for this post.

Note: The IPCC’s new definition of preindustrial, as stated in their Changes to the Underlying Scientific-Technical Assessment to ensure consistency with the approved Summary for Policymakers:

The reference period 1850-1900 is used to approximate pre-industrial global mean surface temperature (GMST).

It’s odd that the IPCC selected those years when not all the climate models used in their 5th assessment report (those stored in the CMIP5 archive) for simulations of past and future climates extend back to 1850. Some only extended back to 1861. Then again, no one expects the IPCC to be logical because they’re a political, not scientific, entity.

Luckily, the ensemble members that meet the criteria of this post do extend back to 1850. So we’ll use the ensemble member outputs for the full IPCC-defined preindustrial period of 1850 to 1900 for this post.

ACCORDING TO THE CMIP5-ARCHIVED CLIMATE MODELS THERE’S A WIDE RANGE OF SIMULATED PREINDUSTRIAL GLOBAL MEAN SURFACE TEMPERATURES

The source of the outputs of the climate model simulations of global mean surface temperature used in this post is the KNMI Climate Explorer. Specifically, as a pre-qualifier, I used the outputs of the simulations of Surface Air Temperatures (TAS) from 90S-90N from the 81 individual ensemble members. From those, I identified the ensemble member with the warmest global mean surface temperature for the preindustrial period and the ensemble member with the coolest global mean surface temperature for the same period. For those who wish to confirm my results, the coolest (lowest average absolute GMST for the period of 1850-1900) is identified as IPSL-CM5A-LR EM-3 at the KNMI Climate Explorer, and the warmest (highest average absolute GMST for the period of 1850-1900) is identified there as GISS-E2-H p3. The average global mean surface temperatures for the other 79 ensemble members during preindustrial times rest between the averages of the two ensemble members.

The outputs of the simulations of global mean surface temperature from those two (the warmest and coolest absolute temperatures) ensemble members for the preindustrial period of 1850-1900 are illustrated in Figure 2, along with their respective period-average global mean surface temperatures for the IPCC-defined preindustrial period of 1850 to 1900 (dashed lines).

Figure 2

As noted at the bottom of the illustration, The Scientists Behind the CMIP5-Archived Models (Used By the IPCC for AR5) Obviously Believe Earth’s Preindustrial Average Surface Temperature Should Be Somewhere Between 12.0 Deg C and 15.0 Deg C. The modelers at the Goddard Institute for Space Studies (GISS) and at the Institut Pierre-Simon Laplace (IPSL) would NOT have archived those models if they hadn’t believed they were of value.

Read the rest of the article here

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