RealClimate logo

Unforced variations: May 2018

Filed under: — group @ 4 May 2018

This month’s (slightly delayed) open thread on climate science topics.

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!]

The Alsup Aftermath

The presentations from the Climate Science tutorial last month have all been posted (links below), and Myles Allen (the first presenter for the plaintiffs) gives his impression of the events.
More »

The Silurian Hypothesis

Filed under: — gavin @ 17 April 2018

One of the benefits of working for NASA is that the enormous range of science the agency covers – from satellite records for the present day, to exoplanet climates, from early Mars and deep time on Earth to the far future – and the opportunity to think ‘big’. This week sees the publication of a paper I wrote with Adam Frank that we hope might provoke some ‘big’ thinking.

The Silurian Hypothesis (preprint) is the idea if industrial civilization had arisen on Earth prior to the existence of hominids, what traces would be left that could be detectable now? As a starting point, we explore what the traces of the Anthropocene will be in millions of years – carbon isotope changes, global warming, increased sedimentation, spikes in heavy metal concentrations, plastics and more – and then look at previous examples of similar events in the geological record. What is unique about our presence on Earth and what might be common to any industrial civilization? Can we rule out similar causes?

More »


  1. G.A. Schmidt, and A. Frank, "The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record?", International Journal of Astrobiology, pp. 1-9, 2018.

Stronger evidence for a weaker Atlantic overturning circulation

Filed under: — stefan @ 11 April 2018

Through two new studies in Nature, the weakening of the Gulf Stream System is back in the scientific headlines. But even before that, interesting new papers have been published – high time for an update on this topic.

Let’s start with tomorrow’s issue of Nature, which besides the two new studies (one of which I was involved in) also includes a News&Views commentary. Everything revolves around the question of whether the Gulf Stream System has already weakened. Climate models predict this will be one consequence of global warming – alongside other problems such as rising sea levels and increasing heat waves, droughts and extreme precipitation. But is such a slowdown already underway today? This question is easier asked than answered. The Atlantic Meridional Overturning Circulation (AMOC, also known as Gulf Stream System) is a huge, three-dimensional flow system throughout the Atlantic, which fluctuates on different time scales. It is therefore by no means enough to put a current meter in the water at one or two points. More »