Judith Curry: Climate Models can't be Trusted !

Climate scientist, based at the Georgia Institute of Technology in Atlanta, Judith Curry reviews the performance of climate models used to predict future temperatures and blame past warming on man's emissions.

She concludes they are "not fit" for the purpose and have failed to predict even the past.

Climate models infer that all of the warming since 1950 can be attributed to humans. However, there have been large magnitude variations in global/hemispheric climate on timescales of 30 years, which are the same duration as the late 20th century warming. The IPCC does not have convincing explanations for previous 30 year periods in the 20th century, notably the warming 1910-1945 and the grand hiatus 1945-1975. Further, there is a secular warming trend at least since 1800 (and possibly as long as 400 years) that cannot be explained by CO2, and is only partly explained by volcanic eruptions.

Given the uncertainties in equilibrium climate sensitivity and the magnitude and phasing of natural internal variability on decadal to century timescales, combined with the failure of climate models to explain the early 20th century warming and the mid-century cooling, I conclude that the climate models are not fit for the purpose of identifying with high confidence the proportional amount of natural versus human causes to the 20th century warming.

As for predicting the future, Curry said the models are "warming too much":

The IPCC’s projections of 21st century climate change explicitly assume that CO2 is the control knob on global climate. Climate model projections of the 21st century climate are not convincing because of:

• Failure to predict the warming slowdown in the early 21st century
• Inability to simulate the patterns and timing of multidecadal ocean oscillations
• Lack of account for future solar variations and solar indirect effects on climate
• Neglect of the possibility of volcanic eruptions that are more active than the relatively quiet 20th century
• Apparent oversensitivity to increases in greenhouse gases

There is growing evidence that climate models are warming too much and that climate sensitivity to CO2 is on the lower end of the range provided by the IPCC...

The 21st century climate model projections do not include:

• a range of scenarios for volcanic eruptions (the models assume that the volcanic activity will be comparable to the 20th century, which had much lower volcanic activity than the 19th century
• a possible scenario of solar cooling, analogous to the solar minimum being predicted by Russian scientists
• the possibility that climate sensitivity is a factor of two lower than that simulated by most climate predictions.
• realistic simulations of the phasing and amplitude of decadal to century scale natural internal variability.

... Hence we don’t have a good understanding of the relative climate impacts of the above or their potential impacts on the evolution of the 21st century climate.

The Way I See It........

It was easy to predict that when 20,000 world leaders, officials, green activists and hangers-on who convened in Paris for the 21st United Nations climate conference, one person you did not see much quoted is Professor Judith Curry. This is a pity. Her record of peer-reviewed publication in the best climate-science journals is second to none, and in America she has become a public intellectual. But on this side of the Atlantic, apparently, she is too ‘challenging’. 

What is troubling about her pariah status is that her trenchant critique of the supposed consensus on global warming is not derived from warped ideology, let alone funding by fossil-fuel firms, but from solid data and analysis.

Some consider her a heretic. According to discredited Professor Michael Mann (the idiot father of the debunked ''Hockey Stick Curve'') who festers at Pennsylvania State University, a vociferous advocate of extreme measures to prevent a climatic Armageddon, she is ''anti-science''.Curry isn’t fazed by the slur.

‘It’s unfortunate, but he calls anyone who doesn’t agree with him a denier,’ she tells me. ‘Inside the climate community there are a lot of people who don’t like what I’m doing. On the other hand, there is also a large, silent group who do like it. But the debate has become hard — especially in the US, because it’s become so polarised.’ Warming alarmists are fond of proclaiming the bullshit fact how 97 per cent of scientists agree that the world is getting hotter, and human beings are to blame. They like to reduce the uncertainties of climate science and climate projections to Manichean simplicity. They have managed to eliminate doubt from what should be a nuanced debate about what to do.

Professor Curry, does not dispute that human-generated carbon dioxide warms the planet. But, she says, the evidence suggests this may be happening much more slowly than the alarmists fear.

UPDATE:  Meanwhile, the obsessive focus on CO2 as the driver of climate change means other research on natural climate variability is being neglected. For example, solar experts believe we could be heading towards a ‘grand solar minimum’ — a reduction in solar output (and, ergo, a period of global cooling) similar to that which once saw ice fairs on the Thames. ‘The work to establish the solar-climate connection is lagging.’