Arguments
How the IPCC is more likely to underestimate the climate response
What the science says...
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Numerous papers have documented how IPCC predictions are more likely to underestimate the climate response. |
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Climate Myth...
IPCC is alarmist
"Unquestionably, the U.N. Intergovernmental Panel on Climate Change (IPCC) was formed to build the scientific case for humanity being the primary cause of global warming. Such a goal is fundamentally unscientific, as it is hostile to alternative hypotheses for the causes of climate change." (Roy Spencer)
"Unquestionably, the U.N. Intergovernmental Panel on Climate Change (IPCC) was formed to build the scientific case for humanity being the primary cause of global warming. Such a goal is fundamentally unscientific, as it is hostile to alternative hypotheses for the causes of climate change."
Climate scientist Roy Spencer made this statement. He starts by suggesting something highly questionable isn’t open to being questioned. What he seeks to do is suggest, by inference, that the IPCC has an agenda, and this distorts the reports they produce. In other words, Spencer (and others) suggest that the IPCC exaggerates what the science says in favour of anthropogenic global warming. It is perfectly legitimate to question this assertion, since Spencer and others offer no evidence to support it.
Some critics go further, suggesting that the IPCC actively suppresses science that doesn’t support the theory that climate change is being caused by human activities. It is notable this ‘other science’ is rarely produced to support the accusation.
Does the IPCC accurately report the findings of science?
The IPCC was formed to report on a broad range of scientific enquiries into the climate, and our effects on it, and to summarise the science for laypeople. The science they summarise is published so it is simple to compare the primary science with the IPCC reports, and compare both to what actually took place.
There are numerous instances where the IPCC reports, which are summaries of published climate change science, have understated the case - hardly suggesting exaggeration in pursuit of an agenda. Here are some examples:
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CO2 output from fossil fuels: observed emissions are close to the worst-case projections made by the IPCC, despite them offering a range of potential emission scenarios. (In fact, atmospheric CO2 is increasing ten times faster than any rate detected in ice core data over the last 22,000 years).
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Sea-level rise is accelerating faster than the IPCC predicted. Actual sea-level rise is 80% higher than the median IPCC projection. By 2100 sea-level rise was predicted by the IPCC to be in the range of 18-59 cm. It is now believed that figure may be far too low, because estimates of contributions from Greenland and Antarctic ice-caps were excluded from AR4 because the data was not considered reliable. (This omission hardly supports the notion that the IPCC seeks to exaggerate global warming trends).
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Each Arctic summer, sea-ice is melting faster than average predictions in the last IPCC report. The Arctic is experiencing a long-term loss of multi-year ice which is also accelerating.
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The body of scientific literature has consistently shown that human greenhouse gas emissions are responsible for more global surface warming than has been observed over the past half century, whereas the IPCC only says that greenhouse gases are responsible for "most" observed warming over this timeframe.
In many similar cases, the evidence suggests that changes in climate are occurring faster, and with more intensity, than the IPCC have predicted. It is not credible to suggest the reports were biased in favour of the theory of anthropogenic global warming when the evidence demonstrates the IPCC were, in fact, so cautious.
In fact, there is evidence however to suggest that the exact opposite is actually the case, both in terms of the scientific evidence itself (see below) and the way the work of the IPCC is reported. A recent study (Freudenburg 2010) investigated what it calls 'the Asymmetry of Scientific Challenge', the phenomenon in which reports on science fail to evaluate all outcomes, favoring certain probabilities while ignoring others. They found that "...new scientific findings were more than twenty times as likely to support the ASC perspective [that disruption through AGW may be far worse than the IPCC has suggested] than the usual framing of the issue in the U.S. mass media".
Claims that the IPCC is alarmist are not supported by evidence, and there are clear indications that the opposite may be the case.
Basic rebuttal written by GPWayne
Update July 2015:
Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial
Last updated on 5 July 2015 by skeptickev. View Archives
[DB] It is very obvious from recent discussions that your quotation above is still invalid. The intercontinental reach & dispersion of aerosols has been amply demonstrated.
Either finish your homework from comments 81 and 94 above or cede those points by declaring your position invalid.
Off-topic diversion snipped.
[DB] Actually, your original assertion about aerosols was made here and was this:
"Has anybody actually investigated further, for example the findings on Aerosols and why the IPCC believe what the range of aersol forcing is thats stated in their 4AR?"
You did not make the assertion about aerosols that you claim until 4 ½ hours later, here.
[DB] This has gone on long enough. As has been noted several times already, finish the work you have claimed for yourself in comments 81 and 94 above. You will be allowed no further podium to waste the time of others here until that work is completed.
Argumentative and sloganeering snipped.
Hi all,
This may be a dumb question, but I'm wondering if someone could clear up my confusion about the rate of change in CO2 concentrations we're seeing today vs. the rate at which they've varied in the past.
In this video, Michael Mann states that the rates today are changing a million times faster than what we've seen in the past, but this article above states that "atmospheric CO2 is increasing ten times faster than any rate detected in ice core data over the last 22,000 years."
Thanks for your help,
Andrew
Woops, forgot the link: http://www.motherjones.com/blue-marble/2013/05/michael-mann-hockey-stick-climate-desk-live
Tough to say, Andrewii. While it's true that CO2 hasn't increased as rapidly as present in at least 300 million years, it would take some selectivity to make the math come out right on "1,000,000 times faster." For example, we could find a period where CO2 advanced 120ppm over the course of 150,000,000 years. Such a period might be found if one used the right analysis (e.g COPSE). Then one could say, "We've put up 120ppm in 150 years, one million times as fast as in period x." Or one could go the other route and find a much shorter period with a much more neutral trend. Without knowing the comparison period, it's hard to say what Mann is referring to.
It's hard to be alarmist with the rate of CO2. As Honisch et al. point out, it's possible there's no precedent for the current rate of increase.
Andrewwii, when studying climate topics and associated facts, try not to view or read individual statements out of the larger context (note also that the video is pasted together from a longer one). It is easy to cherry-pick a single statement taken out of context and get confused by it, or even take it to mean somebody is dishonest or similar.
In this particular case, we are talking about a rise from a preindustrial level of 280 ppm to today's 400 ppm in roughly 200 years (average 1.2 ppm per year, accelerating; currently 2 ppm/yr). In that video, Michael Mann refers to the last time the CO2 level was that high (several million years ago) and how much time it took then to change average levels by roughly as much (e.g. by 100 ppm), "10s of millions of years" (long-term average data here). Taking an average slope (ppm CO2 change over time) from that graph over the last 100 million of years gives roughly 10 ppm/million years ((1300-300) / 100), so about a 5th to a 10th of a million times as fast as today. If you take a shorter period, say only the last 30 million years, the slope is less, nearly matching what Mann referred to.
So you see, it is easy to accuse him of saying something wrong. Human nature. It is more difficult though to stand back, look at the bigger picture, ask a clarifying question if possible, and avoid taking things out of context. So thanks for asking.