The United Nations Intergovernmental Panel on Climate Change (IPCC) boldly declared in its Fourth Assessment Report (AR4) in 2007, “Most of the observed increase in global average temperatures [GAT] since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas [GHG] concentrations.” That conclusion rested in no small measure on another conclusion: variations in the Sun’s activity had little impact on global average temperature.
On the basis of those two conclusions, the IPCC wants developed-country governments to commit to
- $100 billion per year to “reparations” for harm that warming caused by their GHG emissions has caused to developing nations;
- trillions of dollars over the remainder of this century trying to mitigate global warming by switching from low-cost, high-reliability carbon-based fuels (coal, oil, natural gas) to high-cost, low-reliability renewable energy sources (mostly wind and solar); and
- significant reductions in freedom as climate-control bureaucracies take control of more and more of the world’s economy.
Now, however, the Fifth Assessment Report (AR5), due out next year but leaked on December 13, contains a paragraph that puts the IPCC’s whole house of cards at risk:
Many empirical relationships have been reported between GCR [Galactic Cosmic Radiation] or cosmogenic isotope archives and some aspects of the climate system (e.g., Bond et al., 2001; Dengel et al., 2009; Ram and Stolz, 1999). The forcing from changes in total solar irradiance alone does not seem to account for these observations, implying the existence of an amplifying mechanism such as the hypothesized GCR-cloud link. …
Translated into laymen’s language, this means AR4’s conclusion that variations in the Sun’s activity had little impact on GAT was unjustified. It follows that AR4’s more grandiose and policy-relevant conclusion that mostof the observed increase in GAT since 1950 is due to anthropogenic GHG emissions is also unjustified.
Within days the leak generated widespread discussion in the blogosphere.
One of the authors of that bombshell paragraph, Steven Sherwood, disagreed with leaker Alec Rawls’s inference that solar variability could have played a much bigger role, and consequently enhanced CO2 concentration a much smaller role, than AR4 claimed, but Rawls responded (see also here) persuasively that Sherwood’s argument amounted to “inverting the scientific method.” Pointing out that the correlation between atmospheric CO2 concentration and GAT is weak but that the correlation between solar variability and GAT is strong, Rawls wrote:
Sherwood is trying to use theory—his dissatisfaction with a particular theory of how solar amplification might work—to dismiss the evidence that some mechanism of solar amplification must be at work. The bad professor is inverting the scientific method, which requires that evidence always trump theory. If evidence gives way to theory it is not science. It is anti-science. It is the exact opposite of science. [emphases added]
This new admission of natural effects, especially solar, on climatic warming, combined with recent reports demonstrating the lack of strong influence on temperature by carbon dioxide, gives renewed cause to challenge the science behind catastrophic, anthropogenic global warming (CAGW).
The leaked draft contains at least three other major upsets for CAGW alarmists.
First, it concludes that we don’t know enough to say that global warming will increase the frequency or severity of droughts, hurricanes, and floods. Climate scientist Roger Pielke Jr. Tweets, “IPCC AR5 draft shows almost complete reversal from AR4 on trends in drought, hurricanes, floods and is now consistent with scientific literature.”
Second, this prominent graph from it, titled “Estimated changes in the observed globally and annually averaged surface temperature (in °C) since 1990 compared with the range of projections from the previous IPCC assessments,” shows that observed GAT has consistently been toward the low end of model projections.
Third, this graph from it, titled “Observed globally and annually averaged methane concentrations in parts per billion (ppb) since 1990 compared with projections from the previous IPCC assessments,” shows that observed atmospheric methane concentration has consistently fallen below even the lowest model projections.
Those last two points, like the one showing that solar variations play a larger role in GAT than the IPCC has claimed, drive home a point climate skeptics have been making for decades: that empirical observation must trump computer models. Indeed, model output isn’t data; it’s hypothesis, to be tested by observation and, if contradicted by observation, rejected.
When considering how to respond to global warming, we must ask five questions:
- Has GAT risen since some predetermined date when we can say it was “cool” (usually this is c. 1850)? The answer is yes, as far as can be measured; if the answer were “no” we probably wouldn’t be having this conversation.
- If GAT has risen, how much of the rise can be attributed to man’s emissions of GHGs, especially carbon dioxide, compared to natural variables? This is the point of contention currently discussed, and no real consensus exists.
- If man is the cause of some warming, is that amount dangerous? This is also debated, thoughscientific models of climactic change, new trends in the AR5, and real considerations of wealth would suggest the answer is no.
- If man is causing GAT to increase dangerously, can we prevent it? A recent report by the Science and Public Policy Institute concludes that we cannot.
- If man is causing dangerous warming but could prevent it, would the benefits of prevention exceed the costs? Numerous reports like this and this say no. People will benefit much more from economic development than from climate mitigation, which slows economic development.
Given our obligation to protect the poor from harm, the Cornwall Alliance will continue to expose the deficiencies of CAGW science and economics and to oppose costly energy and economic policies in the name of preventing global warming.
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