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Blazer Bob wrote: ..." So, don’t sell your beachfront property just yet.
Beginning back in 1988, certain scientists have been predicting climate doom, some of which should already be evident. That was the year when James Hansen, then the head of the NASA Goddard Institute for Space Studies, testified before Congress that the greenhouse effect was causing warming on Earth and that man was at least partially responsible for it.
“Global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and observed warming,” Hansen told Congress. “It’s already happening now.”
Hansen and fellow scientist Michael Oppenheimer reported that if the buildup of carbon dioxide and methane continued at the current rate, the Earth would be between three and nine degrees Fahrenheit warmer by the years 2025-2050, and that sea levels would rise between one and four feet in the same time frame.
Now, of course it’s not 2025 yet, but that’s only seven years in the future, and unless Hansen and Oppenheimer predicted that the warming would happen all at once (they didn’t), their predictions don’t seem to panning out, as global temperature has risen only slightly more than 0.5° F in that time."...
What were the temperature trends predicted and what were the trends observed? The simulations were run in 1984 or so, and that seems a reasonable beginning date for a trend calculation through to the last full year available, 2017. The modeled changes were as follows:
Scenario A: 0.33±0.03ºC/decade (95% CI)
Scenario B: 0.28±0.03ºC/decade (95% CI)
Scenario C: 0.16±0.03ºC/decade (95% CI)
The observed changes 1984-2017 are 0.19±0.03ºC/decade (GISTEMP), or 0.21±0.03ºC/decade (Cowtan and Way), lying between Scenario B and C, and notably smaller than Scenario A. Compared to 10 years ago, the uncertainties on the trends have halved, and so the different scenarios are more clearly distinguished. By this measure it is clear that the scenarios bracketed the reality (as they were designed to), but did not match it exactly. Can we say more by looking at the details of what was in the scenarios more specifically? Yes, we can.
Thirty years ago, James Hansen testified to Congress about the dangers of human-caused climate change. In his testimony, Hansen showed the results of his 1988 study using a climate model to project future global warming under three possible scenarios, ranging from ‘business as usual’ heavy pollution in his Scenario A to ‘draconian emissions cuts’ in Scenario C, with a moderate Scenario B in between.
Changes in the human effects that influence Earth’s global energy imbalance (a.k.a. ‘anthropogenic radiative forcings’) have in reality been closest to Hansen’s Scenario B, but about 20–30% weaker thanks to the success of the Montreal Protocol in phasing out chlorofluorocarbons (CFCs). Hansen’s climate model projected that under Scenario B, global surface air temperatures would warm about 0.84°C between 1988 and 2017. But with a global energy imbalance 20–30% lower, it would have predicted a global surface warming closer to 0.6–0.7°C by this year.
The actual 1988–2017 temperature increase was about 0.6°C. Hansen’s 1988 global climate model was almost spot-on.
FNP wrote: For those of you interested in the Hansen testimony, it can be found in the Congressional Record of the Senate Committee on Energy and Natural Resources hearing on June 23, 1988. All 222 pages of it.