Thursday, 18 February 2010

Replies to questions about climate science

One Terry today at The Australian asked some questions. Unfortunately the paper is a lousy forum to conduct a conversation because it updates slowly and is patchy in posting comments. Also, Terry, the answers to your questions are readily available. It’s not my fault if Australia’s only national daily doesn’t report science much above the level of superstition and rumour. I would offer my humblest grovelling apologies if it were my fault. For that, you must go to Mr Murdoch.

Tom Clark, Philip Machanick, Sancho, et al

Why not settle the discussion and show us sceptics the proof for the following:
1. That current anthropogenic CO2 emissions are the major cause of global warming. Bear in mind that the physics shows that the amount of warming from CO2 decreases as the concentration increases. Thus there has to be a huge forcing, what is it?
2. That the minimal warming from anthropogenic CO2 causes climate change. Please detail which elements of the climate (storms, drought, heat, floods, tornadoes, etc.) are changing, and the proof that the major cause is anthropogenic CO2.
3. The earth has been warmer in its recent past (Roman and Medieval periods), and these warm periods were very beneficial to mankind. Thus if (and it’s a big if) anthropogenic CO2 has any real influence on the global temperature, why should we be concerned about living in temperatures that existed, to the benefit of mankind, in the past 2000 years?

When you answer, bear in mind that computer predictions are not science.
Also the recent (30 years) global temperature readings are badly compromised, not least from the fact that the original 6000 measuring sites have been reduced to 1500, and it wasn’t the warmest locations that were removed.

Just this once, I’ll do your homework for you. But listen up: you can find all this stuff yourself. The trick is to use Google Scholar, rather than regular Google, which turns up masses of dross. Unfortunately a good fraction of the research literature is paywalled, but NASA makes all theirs public so I will use them disproportionately so you can check my sources. I include a few paywalled papers where the important detail is in the free to view abstract.

1. Scientists have known since the 19th century that the relationship between CO2 concentration and warming is logarithmic. Please don’t parade this fact as evidence of the ignorance of scientists, but rather as evidence of your ignorance of the mainstream. Forcing per doubling of CO2 is 4W/m2 [Hansen et al. 2005]. To put this into context, a 2% increase in solar irradiance adds about 4W/m2 [Hansen et al. 2008]. A 24 W/m2 increase in solar irradiance only over summer, accompanied by a 4-day increase in the duration of summer, caused by a change in axial tilt [Huybers 2006], is enough to tip the earth out of an ice age, so 4W/m2 is a big change – especially as it’s not limited to one season and a limited part of the planet. The maximum variance in solar irradiance since satellite records began is 0.36%, less if you smooth the data to take into account that the biggest variations are very short-term (graph below from TSI Composite Database plot of data 1978-1999). There is no known theory of climate that can use solar variability and other natural influences to reproduce temperature variation since the 1950s. We can only reproduce the trend by models that include natural influences and anthropogenic warming.

2. No serious climate scientist is claiming that the current level of warming is resulting in major increases in storms etc. Yet. There are however measurable effects like loss of Greenland and Antarctic ice mass [Velicogna 2009 – see figures from this paper below] – and many others like glacier retreat, change in species range, and accelerated rates of extinction. You can find plenty of evidence for these if you look. If you want catastrophic effects before you accept firm evidence of climate change, you’re crazy. Predictable effects such as shrinking glaciers are enough for me, especially as many of these metrics are happening faster than predicted.

Antarctic Ice Loss (blue data points: unfiltered)Greenland Ice Loss (blue data points: unfiltered)

3. The evidence of warming in the Medieval Warm Period is patchy and unreliable, and recent evidence suggests the warming was not as fast as that at present [Loso et al. 2007]. A conspiracy-theoretic site styling itself “CO2 science” has an extensive archive of papers purporting to support a globally warmer period in medieval times. I examined the papers they claimed had the highest-quality evidence, and found the temperature peaks varied by as much as 600 years in different locations around the world. That is not a globally warm period. I haven’t seen the evidence that Europe was warmer in Roman times than it is now; there certainly is unlikely to be solid evidence of warming on a worldwide scale for the simple reason that the resolution of our methods of measuring temperature is poor that far back in time. In any case, “warmer” is a relative term. Our current temperatures are on the back of greenhouse warming that hasn’t concluded. Even if we do not add more CO2 to the atmosphere, we have another 0.5°C of warming or so due from slower feedbacks. The Roman world and Medieval Europe may have benefited from local warming from a sub-optimal climate for agriculture to a better climate for agriculture. Warming today is unlikely to have that effect: much of the world’s rice crop for example is grown at close to its temperature limits for high yields, a concern for food production in China [Tao et al. 2006].

On your other comments, if computer predictions aren’t science, we are going to have to stop doing biology and most other branches of modern science. Computer models are no different than mathematical models, except they can process a lot of information fast. Like mathematical models, they can be wrong. This is why scientists check on each other, and build their own models from scratch, rather than rely on a popular model to be correct.

The claim that measurements are compromised by reduction in climate stations is rubbish, especially the claim that the removed sites were from cooler areas. Temperature measurements are not in absolute readings, but anomalies, deviations from a baseline. The baseline for each weather station is based on typical measurements for that type of station. The number used from each station in the overall temperature calculation is not its temperature but its difference from the baseline. This method was introduced for several reasons, one of which is to avoid exactly the sort of problem to which you allude. NASA documents their approach in detail and provides all the computer programs and data. Check it yourself.

 I have a question for you now:

If climate science really is junk, why is it necessary to oppose it with vaudeville acts, personal attacks, stealing email and clear and obvious lies?

And if you agree with me is that science is about supporting theories with evidence, not personal attack and harassing scientists with whom you disagree, sign my petition.


[Hansen et al. 2005] Hansen, J., Mki. Sato, R. Ruedy, L. Nazarenko, A. Lacis, G.A. Schmidt, G. Russell, I. Aleinov, M. Bauer, SS. Bauer, N. Bell, B. Cairns, V. Canuto, M. Chandler, Y. Cheng, A. Del Genio, G. Faluvegi, E. Fleming, A. Friend, T. Hall, C. Jackman, M. Kelley, N. Kiang, D. Koch, J. Lean, J. Lerner, K. Lo, S. Menon, R. Miller, P. Minnis, T. Novakov, V. Oinas, Ja. Perlwitz, Ju. Perlwitz, D. Rind, A. Romanou, D. Shindell, P. Stone, S. Sun, N. Tausnev, D. Thresher, B. Wielicki, T. Wong, M. Yao, and S. Zhang 2005. Efficacy of climate forcings. J. Geophys. Res. 110, D18104, doi:10.1029/2005JD005776
[Hansen et al. 2008] Hansen, J., Mki. Sato, P. Kharecha, D. Beerling, R. Berner, V. Masson-Delmotte, M. Pagani, M. Raymo, D.L. Royer, and J.C. Zachos, 2008: Target atmospheric CO2: Where should humanity aim? Open Atmos. Sci. J., 2, 217-231, doi:10.2174/1874282300802010217
[Huybers 2006] Peter Huybers. Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing, Science 313 (5786), 508, 28 July. [DOI: 10.1126/science.1125249]
 [Loso et al. 2007] MG Loso, RS Anderson, SP Anderson, PJ Reimer, P J. Sediments Exposed by Drainage of a Collapsing Glacier-Dammed Lake Show That Contemporary Summer Temperatures and Glacier Retreat Exceed the Medieval Warm Period in Southern Alaska, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract PP44A-01
[Tao et al. 2006] Fulu Tao, Masayuki Yokozawa, Yinlong Xu, Yousay Hayashi, Zhao Zhang, Climate changes and trends in phenology and yields of field crops in China, 1981-2000, Agricultural and Forest Meteorology, Volume 138, Issues 1-4, 29 August, Pages 82-92, ISSN 0168-1923, DOI: 10.1016/j.agrformet.2006.03.014
[Velicogna 2009] I Velicogna. Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE, Geophys. Res. Lett., 36, L19503, doi:10.1029/2009GL040222


Unknown said...

I followed this link from RealClimate so am not a regular to your blog. I think this is a very good explanation of some very pertinent issues that are often misunderstood. I am not a climate scientist, although I do have considerable background concerning modelling of complex natural systems under large uncertainty (nuclear waste safety over geological time scales). One thing that bothers me about the public perception of computer modelling in general and climate science in particular, is well reflected in the question from "Terry". That is: most commentators who disparage the use of models in science do not really understand their mode of use.

The public perception, by and large, appears to be formed by the headline grabbing predictive models (forward modelling) that are core to many of the arguments for mitigation. What people don't realise is that modelling is also used in a "forensic accounting" mode (inverse modelling) to establish magnitudes and bounds of uncertain parameters, to guide thinking along new lines of investigation, and to partially quantify the role of poorly understood processes. If scientists were to more frequently characterise this mode of modelling as a kind of highly sophisticated accounting ledger rather than a crystal ball looking into the future, then I think much of the negativity surrounding the term "model" might evaporate or at least be more nuanced.

Philip Machanick said...

Maybe so but the predisposition to disbelieve the science is founded in an inability to accept there can be a decent lifestyle without plentiful cheap fossil fuels. So thinking of better ways to explain the science is limited in its usefulness.

Unknown said...

Agreed. Ideology frequently overwhelms evidence-based and reasoned advice.

(You might also want to delete the last message in Japanese. I just ran it through google translate and was surprised at what it actually meant)

Philip Machanick said...

Thanks, James. I usually catch spam pretty fast on new articles; this sort of abuse is why I moderate comments on articles more than 10 days old.

Nicco said...

Excellent to see a direct and referenced response to these questions. My concern is that the complexity of the science and even the language in trying to explain it baffles the average punter. It is much easier for the punter to accept that the questions (such as "Can you prove that CO2 cause climate change?") cannot be answered, rather than squeezing their brain to try to understand the underpinning science. In any case the skeptics seem to just keep asking the same question over and over until those with the knowledge to answer get sick of answering.

Thankyou for keeping the energy to respond to the same oft repeated questions from climate skeptics.

Keep up the good work.

Anonymous said...

Your number 2 response is incorrect, there certainly has been predictions of intensification of storms.

Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment
P. J. Webster,1 G. J. Holland,2 J. A. Curry,1 H.-R. Chang1

Storms of My Grandchildren - James Hansen

for example.

Glaciers except for the LIA have been receding on average since the last ice age, and don't forget the embarrassment of the IPCC on it's glacier predictions.

Marcel Kincaid said...

Why not settle the discussion and show us sceptics the proof for the following

Of course that will settle nothing, as the answers have been given over and over again . Terry is no different from those "evolution skeptics" who ask how evolution could be true since it violates the 2nd law of thermodynamics, and where's the proof that humans evolved from monkeys (and if they did, why are there still monkeys). These people never change their views, regardless of how many times their mistakes are pointed out.

Philip Machanick said...

Anonymous, the Webster et al. paper suggests there may be a connection between increased storms and increased SST. It does not make a strong enough connection that it invalidates what I wrote. There are predictions that increased storms may arise, but no one is saying in any academic paper I've read that there is conclusive evidence that we are there yet. Please read what I said, and note the word "Yet". Hansen is predicting more extreme storms, but he is not saying were are there now.

The point I was addressing was the assertion that we should see evidence of these events now. If you can find a paper that supports that point, I'll be happy to review it but for now, the original assertion looks to me like a straw argument.