Groeiende twijfel over invloed van de mens op het klimaat

De Amerikaanse klimatologe Judith Curry getuige in hoorzitting Congres.

In de klimaatdiscussie speelt de Amerikaanse klimatologe Judith Curry een opmerkelijke rol. Aanvankelijk volgde zij de mainstream en was zij aanhanger van de menselijke broeikashypothese (AGW = 'Anthropogenic Global Warming'). Toen zij echter voor zichzelf begon na te denken, groeide bij haar de twijfel. Thans probeert zij bruggen te bouwen tussen protagonisten en antagonisten van AGW. Haar autoriteit wordt zowel door voor– als tegenstanders van AGW erkend.

Onlangs trad zij op in een hoorzitting van het Amerikaanse congres. Ik pik een aantal elementen uit haar uiterst zorgvuldig geformuleerde verklaring.

Judith Curry:

The central issue in the scientific debate on climate change is the extent to which the recent (and future) warming is caused by human-caused greenhouse gas emissions versus natural climate variability that are caused by variations from the sun, volcanic eruptions, and large-scale ocean circulations.

Recent data and research supports the importance of natural climate variability and calls into question the conclusion that humans are the dominant cause of recent climate change. This includes
◾ The slow down in global warming since 1998
◾ Reduced estimates of the sensitivity of climate to carbon dioxide
◾ Climate models that are predicting much more warming than has been observed so far in the 21st century

While there are substantial uncertainties in our understanding of climate change, it is clear that humans are influencing climate in the direction of warming. However this simple truth is essentially meaningless in itself in terms of alarm, and does not mandate a particular policy response.

We have made some questionable choices in defining the problem of climate change and its solution:
◾ The definition of ‘dangerous’ climate change is ambiguous, and hypothesized catastrophic tipping points are regarded as very or extremely unlikely in the 21st century.
◾ Efforts to link dangerous impacts of extreme weather events to human-caused warming are misleading and unsupported by evidence.
◾ Climate change is a ‘wicked problem’ and ill-suited to a ‘command and control’ solution.
◾ It has been estimated that the U.S. national commitments to the UN to reduce emissions by 28% will prevent three hundredths of a degree centigrade in warming by 2100.

The inadequacies of current policies based on emissions reduction are leaving the real societal consequences of climate change and extreme weather events largely unadressed, whether caused by humans or natural variability.

The wickedness of the climate change problem provides much scope for disagreement among reasonable and intelligent people. Effectively responding to the possible threats from a warmer climate is made very difficult by the deep uncertainties surrounding the risks both from the problem and the proposed solutions.

The articulation of a preferred policy option in the early 1990’s by the United Nations has marginalized research on broader issues surrounding climate variability and change and has stifled the development of a broader range of policy options. ….

Etc.

Lees verder hier.

Haar verklaring kan hier worden bekeken (vanaf 15.30; voor beantwoording van vragen vanaf 47.30).

Haar verklaring heeft aanleiding gegeven tot een aantal vervolgvragen, zie zij op haar blog heeft beantwoord. Ik pik er een aantal uit:

1. President Obama has warned that, “for the sake of our children and our future, we must do more to combat climate change.” He said we must “choose to believe in the overwhelming judgment of science – and act before it is too late.”

A. Is there an overwhelming judgment of science or any science, showing that the President’s regulatory actions will prevent the threat that he is so concerned about?

If you believe the climate models, then President Obama’s INDC commitment (total of 80% emissions reduction by 2050), then warming would be reduced by 0.011 degrees Centigrade, a number that was provided to me by Chip Knappenberger of CATO using the MAGICC model with an equilibrium climate sensitivity of 3.0oC … If the climate models are indeed running too hot, then the warming would be reduced by an even smaller number.

2. We have heard a lot of doomsday scenarios about what will happen if we do nothing on climate change. However, there has been less attention to what the results of any actions we take to combat climate might be.

A. Suppose we cut all greenhouse gas emissions in the United States. Would this avert the supposed catastrophic impacts?

Eliminating all U.S. greenhouse gas emissions by 2050 would reduce the warming by 0.014oC (as per the EPA MAGICC model). This is an amount of warming that is much smaller than the uncertainty in even measuring the global average temperature.

3. Dr. Curry, what happens to academics who step out of line on climate change?

A. Why would experts be afraid to question climate change orthodoxy?

The censure of scientists disagreeing with the IPCC consensus was particularly acute during the period 2005-2010. As revealed by the Climategate emails, there was a cadre of leading climate scientists that were working to sabotage the reviews of skeptical research papers (and presumably proposals for research funding). Further, scientists challenging climate change orthodoxy are subjected to vitriolic treatment in news articles, op-eds and blogs, damaging the public reputation of these scientists. I have heard from numerous scientists who are sympathetic to my efforts in challenging climate change orthodoxy, but are afraid to speak out or even publish skeptical research since they are fearful of losing their job.

Since 2010, things have improved somewhat especially in Europe; I think this has largely been due to reflections following Climategate and the fact that disagreement about climate change is not as starkly divided along the lines of political parties (i.e. the issue is somewhat less politicized). In the U.S., with President Obama’s recent pronouncements about climate denial and climate deniers (as anyone who does not agree with the consensus) has increased the toxicity of the environment (both academic and public) for scientists that question the IPCC consensus on climate change.

Etc.

Aldus Judith Curry.

Lees verder hier.

De bijdrage van Judith Curry aan het herstel van de integriteit van de klimatologie kan nauwelijks worden overschat.

Voor mijn eerdere DDS–bijdragen zie hier.