There is no one piece of evidence for AGW, and never has been.
Actually there is, or rather there is supposed to be. I'm surprised you don't know about it.
1)
heliogenic.blogspot.com
2)
The UN, in its 2007 climate assessment report, displays a series of plots of predicted rates of temperature change over the decades at altitudes from the Earth’s surface to 30 km, at latitudes from the South Pole via the Equator to the North Pole. Colors are used to illustrate the rates of change in temperature which the UN’s climate models predict, measured in degrees Celsius per decade. Each distinct cause of warming produces a visibly-distinct plot.
Six causes of atmospheric warming are considered. First, plots of natural warming caused by changes in total incoming solar radiation and changes in volcanic activity are shown, followed by plots of anthropogenic warming caused by emissions of greenhouse gases, changes in tropospheric and stratospheric ozone concentration, and the radiative forcing caused by sulphate aerosol particles (which actually cause cooling). Finally, the five plots of predicted warming are combined to create a single, sixth plot.
It is at once visible that the predicted warming caused by greenhouse-gas concentrations produces a pattern strongly distinct from other causes of warming. A “hot spot” appears between 8km and 12km of altitude in or near the tropics. At this computer-predicted “hot spot” high above the Earth, the UN’s models project that greenhouse warming will cause temperature to rise over the decades at a rate up to three times faster than at the surface.
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This instantly-recognizable “hot-spot” on the altitude-versus-latitude plot of predicted rates of temperature change is the unmistakable signature or characteristic fingerprint of greenhouse warming which we have been looking for.
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Real-world temperatures in the upper atmosphere have been measured with balloons since at least the 1960's and with microwave satellite sensors since 1979. However, the Hadley Centre’s plot of real-world radiosonde observations does not demonstrate the “global warming hot-spot” at all. The predicted phenomenon is startlingly and entirely absent from the observational record –
The contrast between the five computer models’ predicted signature of greenhouse warming and the Hadley Centre’s plot of observed decadal rates of change in temperature could not be starker. This astonishing result is explicitly confirmed by the UN’s 2007 assessment report, which describes the near-total absence of its own predicted “hot-spot” signature of anthropogenic greenhouse warming in the observed temperature record, but apparently without appreciating its significance –
“9.4.4.1 Observed Changes
“... All data sets show that the global mean and tropical troposphere has warmed from 1958 to the present, with the warming trend in the troposphere slightly greater than at the surface. Since 1979, it is likely that there is slightly greater warming in the troposphere than at the surface, although uncertainties remain in observed tropospheric warming trends and whether these are greater or less than the surface trend. The range (due to different data sets) of the global mean tropospheric temperature trend since 1979 is 0.12°C to 0.19°C per decade based on satellite-based estimates (Chapter 3) compared to a range of 0.16°C to 0.18°C per decade for the global surface warming.”
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Applying Occam’s Razor, the simplest explanation for the discrepancy between theoretical modeling and real-world observation is that the models on which the case for alarm about climate change are based are very substantially overestimating the effect of anthropogenic greenhouse warming on global temperatures. The Climate Change Science Program, however, prefers to assume that it is observation, rather than theory, that is deficient.
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Can the discrepancy between prediction and observation be explained, as the CCSP suggests, by uncertainties in the observed data? The very close correlation between anomalies in tropical outgoing long-wave radiation and anomalies in global lower-troposphere temperatures, taken with the near-total absence of correlation between monotonic increases in CO2 concentration and chaotic temperature anomalies, suggests that it is the computer models, not real-world observations that are likely to be at fault. Ultimately this question can only be resolved by collecting further data: but the CCSP’s predisposition in favor of theoretical modeling and against the results of direct observation is commonplace among official climate-science bodies. Or does the discrepancy arise because the predictions are carried through to equilibrium climate response, while the observations are perforce carried only to a transient response? Professor Lindzen comments that this failure of observation to match prediction cannot be so easily explained, since the transient response would be likely to exceed the equilibrium response. He concludes that no more than about a third of the observed trend at the surface is likely to be due to greenhouse warming, and adds: “This is about as close as one ever gets to proof in climate physics.”
On this analysis, “global warming” is unlikely to be dangerous and extremely unlikely to be catastrophic.
scienceandpublicpolicy.org
3) See the summary:
scribd.com
4)
Can you have a consensus if no one agrees what the consensus is?
January 5, 2009, 10:12 am
Over at the Blackboard, Lucia has a post with a growing set of comments about anthropogenic warming and the tropical, mid-tropospheric hotspot. Unlike many who are commenting on the topic, I have actually read most of the IPCC AR4 (painful as that was), and came to the same conclusion as Lucia: that the IPCC said the climate models predicted a hot spot in the mid-troposphere, and that this hot spot was a unique fingerprint of global warming (”fingerprint” being a particularly popular word among climate scientists).
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OK, pretty straight-forward. The problem is that this hot spot has not really appeared. In fact, the pattern of warming by altitude and latitude over the last thirty years looks nothing like the circled prediction graphs.
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The scientists at RealClimate (lead defenders of the climate orthodoxy) are not unaware that the hot spot is not appearing. They responded about a year ago that 1) The hot spot is not an anthropogentic-specific fingerprint at all, but will result from all new forcings
the pattern really has nothing to do with greenhouse gas changes, but is a more fundamental response to warming (however caused). Indeed, there is a clear physical reason why this is the case - the increase in water vapour as surface air temperature rises causes a change in the moist-adiabatic lapse rate (the decrease of temperature with height) such that the surface to mid-tropospheric gradient decreases with increasing temperature (i.e. it warms faster aloft). This is something seen in many observations and over many timescales, and is not something unique to climate models.
and they argued 2) that we have not had enough time for the hot spot to appear and they argued 3) all that satellite data really has a lot of error in it anyway.
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But here is what makes me crazy: It is quite normal in science for scientists to have a theory, make a prediction based on this theory, and then go back and tweak the theory when data from real physical processes does not match the predictions. There is certainly no shame in being wrong. The whole history of science is about lurching from failed hypothesis to the next, hopefully improving understanding with each iteration.
But the weird thing about climate science is the sort of Soviet-era need to rewrite history. Commenters on both Lucia’s site and at Climate Audit argue that the IPCC never said the hot spot was a unique fingerprint. The fingerprint has become an un-person.
Why would folks want to do this? After all, science is all about hypothesis - experimentation - new hypothesis. Well, most science. The problem is that climate science has been declared to be 1) A Consensus and 2) Settled. But settled consensus can’t, by definition, have disagreements and falsified forecasts. So history has to be rewritten to protect the infallibility of the Pope the Presidium the climate consensus. It’s a weird way to conduct science, but a logical outcome when phrases like “the science is settled” and “consensus” are used as clubs to silence criticism.
climate-skeptic.com
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If skeptics were really interested in posing alternative understandings, they would be developing their own comprehensive theories instead repeating the same old tired arguments over and over and over.
I'm sorry, but its not necessary to have an iron-clad comprehensive alternate theory to criticize or falsify a scientific claim.
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I will not get into yet another fruitless discussion of the alleged "debunking" of the hockey stick. It was based on a complete misunderstanding of what Mann was doing.
You're presenting rewritten history here. Mann's hockey stick was presented as proof of AGW (thats why the 2001 IPCC report included it in its summary section). Till it was debunked.
So along comes strong AGW proponent (and RealClimate.org
founder) Michael Mann of the University of Massachusetts. Mann
electrified the climate world, and really the world as a whole, with his revised temperature reconstruction, shown below, and called “the Hockey Stick.”
Gone was the Little Ice Age. Gone was the Medieval
Warm Period. His new reconstruction shows a remarkably stable, slightly downward trending temperature record that leaps upward in 1900. Looking at this chart, who could but doubt that our current global climate experience
was something unusual and unprecedented. It is easy to look at this chart and say – wow, that must be man-made!
In fact, the hockey stick chart was used by AGW supporters
in just this way. Surely, after a period of stable temperatures, the 20th century jump is an anomaly that seems to point its finger at man (though if one stops the chart at 1950, before the period of AGW, the chart, interestingly, is
still a hockey stick, though with only natural causes).
Based on this analysis, Mann famously declared that the 1990’s were the warmest decade in a millennia and that "there is a 95 to 99% certainty that 1998 was the hottest year in the last one thousand years." (By the way, Mann now denies he ever made this claim, though you can watch him say these exact words in the CBC documentary Global Warming: Doomsday Called Off). If this is not hubris enough, the USAToday
published a graphic, based on Mann’s analysis and which is still online as of this writing, which purports to show the world’s temperature within .0001 degree for every year going back two thousand years!
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However, the real bombshell was dropped on Mann’s work by a couple of Canadian scientists named Stephen McIntyre and Ross McKitrick (M&M). M&M had to fight an uphill battle, because Mann resisted their third party review of his analysis at every turn, and tried to deny them access to his data
and methodology, an absolutely unconscionable violation of the principles of science (particularly publicly funded science). M&M got very good at filing Freedom of Information Act Requests (or the Canadian equivalent)
Eventually, M&M found massive flaws with Mann’s statistical approach, flaws that have since been confirmed by many experts, such that there are few people today that treat Mann’s analysis seriously (<b.At best, his supporters
defend his work with a mantra roughly akin to “fake but accurate.” I’ll quote the MIT Technology Review for M&M’s key finding:
But now a shock: Canadian scientists Stephen McIntyre and Ross McKitrick have uncovered a fundamental mathematical flaw in
the computer program that was used to produce the hockey stick. …
[Mann’s] improper normalization procedure tends to
emphasize any data that do have the hockey stick shape, and to suppress all data that do not. To demonstrate this effect, McIntyre and McKitrick created some meaningless test data that had, on average, no trends. This method of generating random data is called Monte Carlo analysis, after the famous casino,
and it is widely used in statistical analysis to test procedures. When McIntyre and McKitrick fed these random data into the Mann procedure, out popped a hockey stick shape!
A more complete description of problems with Mann hockey stick can be found at this link. Recently, a US Congressional Committee asked a group of independent statisticians led by Dr. Edward Wegman, Chair of the National Science Foundation’s Statistical Sciences Committee, to evaluate the Mann
methodology. Wegman et. al. savaged the Mann methodology as well as the peer review process within the climate community. From their findings:
It is important to note the isolation of the paleoclimate community; even though they rely heavily on statistical methods they do not seem to be interacting with the statistical community. Additionally, we judge that the sharing of research materials, data and results was haphazardly and grudgingly done. In this case we judge that there was too
much reliance on peer review, which was not necessarily independent. Moreover, the work has been sufficiently politicized that this community can hardly reassess their public positions without losing credibility. Overall, our committee believes that Dr. Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis.
In 2007, the IPCC released its new climate report, and the
hockey stick, which was the centerpiece bombshell of the 2001 report, and which was the “consensus” reconstruction of this “settled” science, can hardly be found. There is nothing wrong with errors in science; in fact, science is sometimes advanced the most when mistakes are realized. What is worrying is the unwillingness by the IPCC to acknowledge a mistake was made, and to try to learn from that mistake. Certainly the issues raised with the hockey stick are not mentioned in the most recent IPCC report, and an opportunity to
be a bit introspective on methodology is missed. M&M, who were ripped to shreds by the global warming community for daring to question the hockey stick, are never explicitly vindicated in the report. The climate community slunk away rather than acknowledging error.
coyoteblog.com |
