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Fall AGU Week 2018

Filed under: — gavin @ 11 December 2018

Fall AGU is in Washington DC. Follow #AGU18 for twitter discussions and highlights, and live streaming of keynotes and selected sessions. Use this thread to discuss anything arising from the meeting – or it’s controversies.

4th National Climate Assessment report

Filed under: — gavin @ 23 November 2018

In possibly the biggest “Friday night news dump” in climate report history, the long awaited 4th National Climate Assessment (#NCA4) was released today (roughly two weeks earlier than everyone had been expecting).

The summaries and FAQ (pdf) are good, and the ClimateNexus briefing is worth reading too. The basic picture is utterly unsurprising, but the real interest in the NCA is the detailed work on vulnerabilities and sectorial impacts in 10 specific regions of the US. The writing teams for those sections include a whole raft of scientists and local stakeholders and so if you think climate reports are the same old, same old, it’s where you should go to read things you might not have seen before.

Obviously, since the report was only released at 2pm today without any serious embargo, most takes you will read today or tomorrow will be pretty superficial, but there should be more considered discussions over the next few days. Feel free to ask specific questions or bring up topics below.

The long story of constraining ocean heat content

Filed under: — gavin @ 21 November 2018

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…

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Cracking the Climate Change Case

I have an op-ed in the New York Times this week:

How Scientists Cracked the Climate Change Case
The biggest crime scene on the planet is the planet. We know the earth is warming, but who or what is causing it?
Emilia Miękisz

Many of you will recognise the metaphor from previous Realclimate pieces (this is earliest one I think, from 2007), and indeed, the working title was “CSI: Planet Earth”. The process description and conclusions are drawn from multiple sources on the attribution of recent climate trends (here, here etc.), as well the data visualization for surface temperature trends at Bloomberg News.

There have been many comments about this on Twitter – most appreciative, some expected, and a few interesting. The expected criticisms come from people who mostly appear not to have read the piece at all (“Climate has changed before!” – a claim that no-one disputes), and a lot of pointless counter-arguments by assertion. Of the more interesting comment threads, was one started by Ted Nordhaus who asked

My response is basically that it might be old hat for him (and maybe many readers here), but I am constantly surprised at the number of people – even those concerned about climate – who are unaware of how we do attribution and how solid the science behind the IPCC statements is. And judging by many of the comments, it certainly isn’t the case that these pieces are only read by the already convinced. But asking how many people are helped to be persuaded by articles like this is a valid question, and I don’t really know the answer. Anyone?

IPCC Special Report on 1.5ºC

Filed under: — gavin @ 7 October 2018

Responding to climate change is far more like a marathon than a sprint.

The IPCC 1.5ºC Special report (#SR15) has been released:

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Musing about Losing Earth

The NY Times Magazine has a special issue this weekend on climate change. The main article is “Losing the Earth” by Nathaniel Rich, is premised on the idea that in the period 1979 to 1989 when we basically knew everything we needed to know that climate change was a risk, and the politics had not yet been polarized, we missed our opportunity to act. Stated this way, it would probably be uncontroversial, but since the article puts the blame for this on “human nature”, rather than any actual humans, extensive Twitter discussion ensues…

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Model Independence Day

Filed under: — gavin @ 4 July 2018

We hold these truths to be self-evident, that all models are created equal, that they are endowed by their Creators with certain unalienable Rights, that among these are a DOI, Runability and Inclusion in the CMIP ensemble mean.

Well, not quite. But it is Independence Day in the US, and coincidentally there is a new discussion paper (Abramowitz et al) (direct link) posted on model independence just posted at Earth System Dynamics.

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  1. G. Abramowitz, N. Herger, E. Gutmann, D. Hammerling, R. Knutti, M. Leduc, R. Lorenz, R. Pincus, and G.A. Schmidt, "Model dependence in multi-model climate ensembles: weighting, sub-selection and out-of-sample testing", Earth System Dynamics Discussions, pp. 1-20, 2018.

30 years after Hansen’s testimony

Filed under: — gavin @ 21 June 2018

“The greenhouse effect is here.”
– Jim Hansen, 23rd June 1988, Senate Testimony

The first transient climate projections using GCMs are 30 years old this year, and they have stood up remarkably well.

We’ve looked at the skill in the Hansen et al (1988) (pdf) simulations before (back in 2008), and we said at the time that the simulations were skillful and that differences from observations would be clearer with a decade or two’s more data. Well, another decade has passed!

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  1. J. Hansen, I. Fung, A. Lacis, D. Rind, S. Lebedeff, R. Ruedy, G. Russell, and P. Stone, "Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model", Journal of Geophysical Research, vol. 93, pp. 9341, 1988.

Transparency in climate science

Good thing? Of course.*

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Nenana Ice Classic 2018

Filed under: — gavin @ 1 May 2018

Another year, another ice out date. As in previous years, here’s an update of the Nenana Ice Classic time series (raw date, and then with a small adjustment for the calendrical variations in ‘spring’). One time series doesn’t prove much, but this is of course part of a much larger archive of phenomenological climate-related data that I’ve talked about before.

This year the ice on the Tanana River went out on May 1st, oddly enough the same date as last year, after another very warm (but quite snowy) Alaskan winter.

My shadow bet on whether any climate contrarian site will mention this dataset remains in play (none have since 2013 which was an record late year). [Update: It was mentioned on WUWT!]