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Climate modelling

How good have climate models been at truly predicting the future?

4 Dec 2019 by Gavin

A new paper from Hausfather and colleagues (incl. me) has just been published with the most comprehensive assessment of climate model projections since the 1970s. Bottom line? Once you correct for small errors in the projected forcings, they did remarkably well.

[Read more…] about How good have climate models been at truly predicting the future?

Filed Under: Climate modelling, Climate Science, Greenhouse gases, Instrumental Record, Model-Obs Comparisons, statistics

Sensitive But Unclassified

6 Nov 2019 by Gavin

The US federal government goes to quite a lot of effort to (mostly successfully) keep sensitive but unclassified (SBU) information (like personal data) out of the hands of people who would abuse it. But when it comes to the latest climate models, quite a few are SBU as well.

[Read more…] about Sensitive But Unclassified

Filed Under: Climate modelling, Climate Science, Communicating Climate, Instrumental Record, IPCC

Koonin’s case for yet another review of climate science

15 Jun 2019 by Gavin

We watch long YouTube videos so you don’t have to.

In the seemingly endless deliberations on whether there should be a ‘red team’ exercise to review various climate science reports, Scott Waldman reported last week that the original architect of the idea, Steve Koonin, had given a talk on touching on the topic at Purdue University in Indiana last month. Since the talk is online, I thought it might be worth a viewing.

[Spoiler alert. It wasn’t].

[Read more…] about Koonin’s case for yet another review of climate science

Filed Under: Climate modelling, Climate Science, In the News, Instrumental Record, IPCC, Scientific practice, skeptics

Unforced Variations vs Forced Responses?

6 Jun 2019 by group

Guest commentary by Karsten Haustein, U. Oxford, and Peter Jacobs (George Mason University).

One of the perennial issues in climate research is how big a role internal climate variability plays on decadal to longer timescales. A large role would increase the uncertainty on the attribution of recent trends to human causes, while a small role would tighten that attribution. There have been a number of attempts to quantify this over the years, and we have just published a new study (Haustein et al, 2019) in the Journal of Climate addressing this question.

Using a simplified climate model, we find that we can reproduce temperature observations since 1850 and proxy-data since 1500 with high accuracy. Our results suggest that multidecadal ocean oscillations are only a minor contributing factor in the global mean surface temperature evolution (GMST) over that time. The basic results were covered in excellent articles in CarbonBrief and Science Magazine, but this post will try and go a little deeper into what we found.

[Read more…] about Unforced Variations vs Forced Responses?

References

  1. K. Haustein, F.E.L. Otto, V. Venema, P. Jacobs, K. Cowtan, Z. Hausfather, R.G. Way, B. White, A. Subramanian, and A.P. Schurer, "A Limited Role for Unforced Internal Variability in Twentieth-Century Warming", Journal of Climate, vol. 32, pp. 4893-4917, 2019. http://dx.doi.org/10.1175/JCLI-D-18-0555.1

Filed Under: Aerosols, Climate modelling, Climate Science, Greenhouse gases, Instrumental Record

First successful model simulation of the past 3 million years of climate change

3 Apr 2019 by Stefan

Guest post by Matteo Willeit, Potsdam Institute for Climate Impact Research

A new study published in Science Advances shows that the main features of natural climate variability over the last 3 million years can be reproduced with an efficient model of the Earth system.

The Quaternary is the most recent geological Period, covering the past ~2.6 million years. It is defined by the presence of glacial-interglacial cycles associated with the cyclic growth and decay of continental ice sheets in the Northern Hemisphere. Climate variations during the Quaternary are best seen in oxygen isotopes measured in deep-sea sediment cores, which represent variations in global ice volume and ocean temperature. These data show clearly that there has been a general trend towards larger ice sheets and cooler temperatures over the last 3 million years, accompanied by an increase in the amplitude of glacial-interglacial variations and a transition from mostly symmetry cycles with a periodicity of 40,000 years to strongly asymmetric 100,000-year cycles at around 1 million years ago.  However, the ultimate causes of these transitions in glacial cycle dynamics remain debated.

[Read more…] about First successful model simulation of the past 3 million years of climate change

Filed Under: Carbon cycle, Climate modelling, Climate Science, Paleoclimate

The best case for worst case scenarios

26 Feb 2019 by Gavin

The “end of the world” or “good for you” are the two least likely among the spectrum of potential outcomes.

Stephen Schneider

Scientists have been looking at best, middling and worst case scenarios for anthropogenic climate change for decades. For instance, Stephen Schneider himself took a turn back in 2009. And others have postulated both far more rosy and far more catastrophic possibilities as well (with somewhat variable evidentiary bases).

[Read more…] about The best case for worst case scenarios

References

  1. S. Schneider, "The worst-case scenario", Nature, vol. 458, pp. 1104-1105, 2009. http://dx.doi.org/10.1038/4581104a

Filed Under: Climate impacts, Climate modelling, Climate Science, Communicating Climate, IPCC, Reporting on climate, Scientific practice

Update day

7 Feb 2019 by Gavin

So Wednesday was temperature series update day. The HadCRUT4, NOAA NCEI and GISTEMP time-series were all updated through to the end of 2018 (slightly delayed by the federal government shutdown). Berkeley Earth and the MSU satellite datasets were updated a couple of weeks ago. And that means that everyone gets to add a single additional annual data point to their model-observation comparison plots!

[Read more…] about Update day

Filed Under: Climate modelling, Climate Science, Instrumental Record, Model-Obs Comparisons

New Ocean Heat Content Histories

23 Jan 2019 by group

Guest commentary from Laure Zanna (U. Oxford) and G. Jake Gebbie (WHOI)

Two recent papers, Zanna et al. (2019) (hereafter ZKGIH19) and Gebbie & Huybers (2019) (hereafter GH19), independently reconstructed ocean heat content (OHC) changes prior to the instrumentally-based records (which start ~1950). The goals (and methodologies) of the two papers were quite different – ZKGIH19 investigated regional patterns of ocean warming and thermal sea level rise, while GH19 analyzed the long-term memory of the deep ocean – but they both touch on the same key questions of climate forcing and response.

[Read more…] about New Ocean Heat Content Histories

References

  1. L. Zanna, S. Khatiwala, J.M. Gregory, J. Ison, and P. Heimbach, "Global reconstruction of historical ocean heat storage and transport", Proceedings of the National Academy of Sciences, vol. 116, pp. 1126-1131, 2019. http://dx.doi.org/10.1073/pnas.1808838115
  2. G. Gebbie, and P. Huybers, "The Little Ice Age and 20th-century deep Pacific cooling", Science, vol. 363, pp. 70-74, 2019. http://dx.doi.org/10.1126/science.aar8413

Filed Under: Climate modelling, Climate Science, Greenhouse gases, Instrumental Record, Oceans, Paleoclimate

Bending low with Bated breath

22 Dec 2018 by Gavin

“Shall I bend low and in a bondman’s key,
With bated breath and whisp’ring humbleness…?”

Shylock (Merchant of Venice, Act 1, Scene 3)

As dark nights draw in, the venerable contrarians at the GWPF are still up late commissioning silly pseudo-rebuttals to mainstream science. The latest, [but see update below] which no-one was awaiting with any kind of breath, is by Dr. Ray Bates (rtd.) which purports to be a take-down of the recent #SR15 report. As Peter Thorne (an IPCC author) correctly noted, this report is a “cut-and-paste of long-debunked arguments”. I’ve grown a little weary of diving down to rebut every repetitive piece of nonsense, but this one has a few funny aspects that make it worthwhile to do so.

When they go low, we go “sigh…”.

[Read more…] about Bending low with Bated breath

Filed Under: Climate modelling, Climate Science, Instrumental Record, IPCC, Oceans

The long story of constraining ocean heat content

21 Nov 2018 by Gavin

Scientists predicted in the 1980s that a key fingerprint of anthropogenic climate change would be found in the ocean. If they were correct that increases in greenhouse gases were changing how much heat was coming into the system, then the component with the biggest heat capacity, the oceans, is where most of that heat would end up.

We have now had almost two decades of attempts to characterize this change, but the path to confirming those predictions has been anything but smooth…

[Read more…] about The long story of constraining ocean heat content

Filed Under: Climate modelling, Climate Science, Oceans

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