The “official” GISS set of temperature records (here) comprises surface thermometer records going back to January 1880. It takes a lot of massaging to construct a monthly time series of “global” temperatures that spans 137 years, with spotty coverage of Earth’s surface (even now), and wide variability in site conditions. There’s the further issue of data manipulation, the most recent example of which was the erasure of the pause that had lasted for almost 19 years.
Taking the GISS numbers at face value, for the moment, what do they suggest about changes in Earth’s temperature (whatever that means)? Almost nothing, when viewed in proper perspective. When viewed, that is, in terms of absolute (Kelvin) temperature readings:
Yes, there’s an upward trend of about 1 degree K (or 1 degree C) per century. And, yes, it’s statistically significant. But the statistical significance is due to the strong correlation between time and temperature. The trend doesn’t explain why Earth’s temperature is what it is. Nor does it explain why it has varied over the past 137 years.
Those variations have been minute. The maximum of 288.79K is only 1.1 percent higher than the minimum of 285.68K. This minuscule difference must be swamped by measurement and estimation errors. It is credible that Earth’s average temperature — had it been measured consistently over the past 137 years — would have changed less (or more) than the GISS record indicates. It is credible that the observed uptrend is an artifact of selective observation and interpretation. It has become warmer over the past 30 years where I live, for example, but the warming is explained entirely by the urban heat-island effect.
A proper explanation of the minute variations in Earth’s temperature — if real — would incorporate all of the factors that influence Earth’s temperature, starting from Earth’s core and going out into the far reaches of the universe (e.g., to account for the influence of cosmic radiation). Among many things, a proper explanation would encompass the effects of the expansion of the universe, the position and movement of the Milky Way, the position and movement of the Solar System, and the position and movement of Earth within the Solar System, and variations in Earth’s magnetic field.
But global climate models (or GCMs) focus entirely on temperature changes and are limited to superficial factors that are hypothesized to cause those changes — but only those factors that can be measured or estimated by complex and often-dubious methods (e.g., the effects of cloud cover). This is equivalent to searching for one’s car keys under a street lamp because that’s where the light is, even though the car keys were dropped 100 feet away.
The deeper and probably more relevant causes of Earth’s ambient temperature are to be found, I believe, in Earth’s core, magma, plate dynamics, ocean currents and composition, magnetic field, exposure to cosmic radiation, and dozens of other things that — to my knowledge — are ignored by GCMs. Moreover, the complexity of the interactions of such factors, and others that are usually included in GCMs, cannot possibly be modeled.
- Changes in Earth’s temperature are unknown with any degree of confidence.
- At best, the changes are minute.
- The causes of the changes are unknown.
- It is impossible to model Earth’s temperature or changes in it.
It is therefore impossible to say whether and to what extent human activity causes Earth’s temperature to change.
It is further impossible for a group of scientists, legislators, or opinionizers to say whether Earth’s warming — if indeed it is warming — is a bad thing. It is a good thing for agriculture — up to some point. It’s a good thing for human comfort (thus the flight of “snowbirds”) — up to some point. But for reasons given above, it’s truly unknown whether those points, and others, will be reached. But as they are, human beings will adapt, as they have in the past — unless their ability to adapt is preempted or hampered by costly regulations and counterproductive resource reallocations.
Science is not on the side of the doom-sayers, no matter how loudly they protest that it is.
Related reading (listed chronologically):
Freeman Dyson, “Heretical Thoughts about Science and Society“, from Many Colored Glass: Reflections on the Place of Life in the Universe, University of Virgina Press, 2007
Ron Clutz, “Temperatures According to Climate Models“, Science Matters, March 24, 2015
Dr. Tim Ball, “Long-Term Climate Change: What Is a Reasonable Sample Size?“, Watts Up With That?, February 7, 2016
The Global Warming Policy Foundation, Climate Science: Assumptions, Policy Implications, and the Scientific Method, 2017
John Mauer, “Through the Looking Glass with NASA GISS“, Watts Up With That?, February 22, 2017
George White, “A Consensus of Convenience“, Watts Up With That?, August 20, 2017
Jennifer Marohasy, “Most of the Recent Warming Could be Natural“, Jennifer Marohasy, August 21, 2017
AGW: The Death Knell (with many links to related reading and earlier posts)
Not-So-Random Thoughts (XIV) (second item)
AGW in Austin?
Understanding Probability: Pascal’s Wager and Catastrophic Global Warming
The Precautionary Principle and Pascal’s Wager
AGW in Austin? (II) (with more links to related reading)