RealClimate

Climate science from climate scientists...

You are here: Home / Archives for Climate Science

Climate Science

Model projections and observations comparison page

by

We should have done this ages ago, but better late than never!

We have set up a permanent page to host all of the model projection-observation comparisons that we have monitored over the years. This includes comparisons to early predictions for global mean surface temperature from the 1980’s as well as more complete projections from the CMIP3 and CMIP5. The aim is to maintain this annually, or more often if new datasets or versions become relevant.

We are also happy to get advice on stylistic choices or variations that might make the graphs easier to comprehend or be more accurate – feel free to suggest them in the comments below (since the page itself will be updated over time, it doesn’t have comments associated with it).

If there are additional comparisons you are aware of that you think would be useful to include, please point to the model and observational data set(s) and we’ll try and include that too. We should have the Arctic sea ice trends up shortly for instance.

What is the uncertainty in the Earth’s temperature rise?

by

Guest commentary by Shaun Lovejoy (McGill University)

Below I summarize the key points of a new Climate Dynamics (CD) paper that I think opens up new perspectives on understanding and estimating the relevant uncertainties. The main message is that the primary sources of error and bias are not those that have been the subject of the most attention – they are not human in origin. The community seems to have done such a good job of handling the “heat island”, “cold park”, and diverse human induced glitches that in the end these make only a minor contribution to the final uncertainty. The reason of course, is the huge amount of averaging that is done to obtain global temperature estimates, this averaging essentially averages out most of the human induced noise.

Two tough sources of uncertainty remain: missing data and a poor definition of the space-time resolution; the latter leads to the key scale reduction factor. In spite of these large low frequency uncertainties, at centennial scales, they are still only about 13% of the IPCC estimated anthropogenic increase (with 90% certainty).

This paper is based on 6 monthly globally averaged temperature series over the common period 1880-2012 using data that were publically available in May 2015. These were NOAA NCEI, NASA GISTEMP, HadCRUT4, Cowtan and Way, Berkeley Earth and the 20th Century Reanalysis. In the first part on relative uncertainties, the series are systematically compared with each other over scales ranging from months to 133 years. In the second part on absolute uncertainties, a stochastic model is developed with two parts. The first simulates the true temperatures, the second treats the measurement errors that would arise from this series from three different sources of uncertainty: i) usual auto-regressive (AR)-type short range errors, ii) missing data, iii) the “scale reduction factor”.

The model parameters are fit by treating each of the six series as a stochastic realization of the stochastic measurement process. This yields an estimate of the uncertainty (spread) of the means of each series about the true temperature – an absolute uncertainty – not simply the spread of the series means about their common mean value (the relative uncertainty). This represents the absolute uncertainty of the series means about a (still unknown) absolute reference point (which is another problem for another post).

[Read more…] about What is the uncertainty in the Earth’s temperature rise?

References

  1. S. Lovejoy, "How accurately do we know the temperature of the surface of the earth?", Climate Dynamics, vol. 49, pp. 4089-4106, 2017. http://dx.doi.org/10.1007/s00382-017-3561-9

The true meaning of numbers

by

Gavin has already discussed John Christy’s misleading graph earlier in 2016, however, since the end of 2016, there has been a surge in interest in this graph in Norway amongst people who try to diminish the role of anthropogenic global warming.

I think this graph is warranted some extra comments in addition to Gavin’s points because it is flawed on more counts beyond those that he has already discussed. In fact, those using this graph to judge climate models reveal an elementary lack of understanding of climate data.

Fig. 1. Example of Christy’s flawed evaluation taken from Comparing models to the satellite datasets.

[Read more…] about The true meaning of numbers

Something Harde to believe…

by

A commenter brings news of an obviously wrong paper that has just appeared in Global and Planetary Change. The paper purports to be a radical revision of our understanding of the carbon cycle by Hermann Harde. The key conclusions are (and reality in green):

  • The average residence time of CO2 in the atmosphere is found to be 4 years.

    [The residence time for an individual molecule is not the same as the perturbation response time of the carbon cycle which has timescales of decades to thousands of years.]

  • The anthropogenic fraction of CO2 in the atmosphere is only 4.3%.

    [Actually, it’s 30%.]

  • Human emissions only contribute 15% to the CO2 increase over the Industrial Era.

    [It’s all of it.]

Since these points contradict multiple independent sources of evidence, I can, without hesitation, predict that there are fundament flaws in this paper that will raise serious questions about the quality of the peer-review that this paper went through. Oddly, this paper is labeled as an “Invited Research Article” and so maybe some questions might be asked of the editor responsible too.

Notwithstanding our last post on the difficulty in getting comments published, this paper is crying out for one.

But this kind of thing has been done before, does not require any great sophistication or computer modeling to rebut, and has come up so many times before (Salby (also here), Beck, Segalstad, Jaworowski etc.), that perhaps a crowd-sourced rebuttal would be useful.

So, we’ll set up an overleaf.com page for this (a site for collaborative LaTeX projects), and anyone who wants to contribute should put the gist of their point in the comments and we’ll send the link so you can add it to the draft. Maybe the citizen scientists among you can pull together a rebuttal faster than the professionals?

Update: The crowd-sourced comment has appeared Köhler et al (2018).

References

  1. H. Harde, "Scrutinizing the carbon cycle and CO2 residence time in the atmosphere", Global and Planetary Change, vol. 152, pp. 19-26, 2017. http://dx.doi.org/10.1016/j.gloplacha.2017.02.009
  2. P. Köhler, J. Hauck, C. Völker, D.A. Wolf-Gladrow, M. Butzin, J.B. Halpern, K. Rice, and R.E. Zeebe, "Comment on “ Scrutinizing the carbon cycle and CO 2 residence time in the atmosphere ” by H. Harde", Global and Planetary Change, vol. 164, pp. 67-71, 2018. http://dx.doi.org/10.1016/j.gloplacha.2017.09.015

Someone C.A.R.E.S.

by

Do we need a new venue for post-publication comments and replications?

Social media is full of commentary (of varying degrees of seriousness) on the supposed replication crisis in science. Whether this is really a crisis, or just what is to be expected at the cutting edge is unclear (and may well depend on the topic and field). But one thing that is clear from all the discussion is that it’s much too hard to publish replications, or even non-replications, in the literature. Often these efforts have to be part of a new paper that has to make its own independent claim to novelty before it can get in the door and that means that most attempted replications don’t get published at all.

This is however just a subset of the difficulty that exists in getting any kind of comment on published articles accepted. Having been involved in many attempts – in the original journal or as a new paper – some successful, many not, it has become obvious to me that the effort to do so is wholly disproportionate to the benefits for the authors, and is thus very effectively discouraged.

The overall mismatch between the large costs/minimal benefit for the commenters, compared to the real benefits for the field, suggests that something really needs to change.

I have thought for a long time that an independent journal venue for comments would be a good idea, but a tweet by Katharine Hayhoe last weekend made me realize that the replication issue might be well served by a similar approach. So, here’s a proposal for a new journal.

Commentary And Replication in Earth Science (C.A.R.E.S.)

[Read more…] about Someone C.A.R.E.S.

References

  1. G. Foster, J.D. Annan, G.A. Schmidt, and M.E. Mann, "Comment on “Heat capacity, time constant, and sensitivity of Earth's climate system” by S. E. Schwartz", Journal of Geophysical Research: Atmospheres, vol. 113, 2008. http://dx.doi.org/10.1029/2007JD009373
  2. G.A. Schmidt, "Spurious correlations between recent warming and indices of local economic activity", International Journal of Climatology, vol. 29, pp. 2041-2048, 2009. http://dx.doi.org/10.1002/joc.1831

Serving up a NOAA-thing burger

by

I have mostly been sitting back and watching the John Bates story go through the predictable news-cycle of almost all supposed ‘scandalous’ science stories. The patterns are very familiar – an initial claim of imperfection spiced up with insinuations of misconduct, coordination with a breathless hyping of the initial claim with ridiculous supposed implications, some sensible responses refuting the initial specific claims and demolishing the wilder extrapolations. Unable to defend the nonsense clarifications are made that the initial claim wasn’t about misconduct but merely about ‘process’ (for who can argue against better processes?). Meanwhile the misconduct and data falsification claims escape into the wild, get more exaggerated and lose all connection to any actual substance. For sure, the technical rebuttals to the specific claims compete with balance of evidence arguments and a little bit of playful trolling for the attention of anyone who actually cares about the details. None of which, unfortunately, despite being far more accurate, have the narrative power of the original meme.

The next stages are easy to predict as well – the issues of ‘process’ will be lost in the noise, the fake overreaction will dominate the wider conversation and become an alternative fact to be regurgitated in twitter threads and blog comments for years, the originators of the issue may or may not walk back the many mis-statements they and others made but will lose credibility in any case, mainstream scientists will just see it as hyper-partisan noise and ignore it, no papers will be redacted, no science will change, and the actual point (one presumes) of the ‘process’ complaint (to encourage better archiving practices) gets set back because it’s associated with such obvious nonsense.

This has played out many, many times before: The Yamal story had a very similar dynamic, and before that the ‘1934‘ story, etc. etc.

Assuming for the sake of politeness that sound and fury signifying nothing is not the main goal for at least some participants, the question arises: since this is so predictable why do people still keep making the same mistakes?

[Read more…] about Serving up a NOAA-thing burger

Fake news, hacked mail, alternative facts – that’s old hat for climate scientists

by

Distortion? False information? Conspiracy theories? Hacked email? Climate scientists have known all this for decades. What can be learned from their rich experience with climate propaganda.

The world is slowly waking up. “Post-truth” was declared the word of the year 2016 by the Oxford Dictionaries. Finally, people start to widely appreciate how dangerous the epidemic of fake news is for democracy.

Stir up hate, destroy discourse, make insane claims until no one can distinguish the most bizarre absurdity from the truth any more.

Thus the Austrian author Robert Misik aptly describes the strategy of right-wing populists.

Some call it “alternative facts”. (Those are the convenient alternative to true facts.) Let’s simply call it propaganda. [Read more…] about Fake news, hacked mail, alternative facts – that’s old hat for climate scientists