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Alsup asks for answers

Some of you might have read about the lawsuit by a number of municipalities (including San Francisco and Oakland) against the major oil companies for damages (related primarily to sea level rise) caused by anthropogenic climate change. The legal details on standing, jurisdiction, etc. are all very interesting (follow @ColumbiaClimate for those details), but somewhat uniquely, the judge (William Alsup) has asked for a tutorial on climate science (2 hours of evidence from the plaintiffs and the defendents). Furthermore, he has posted a list of eight questions that he’d like the teams to answer.

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More ice-out and skating day data sets

Filed under: — gavin @ 26 February 2018

The responses to the last post on the Rideau Canal Skateway season changes were interesting, and led to a few pointers to additional data sets that show similar trends and some rather odd counter-points from the usual suspects.
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2017 temperature summary

Filed under: — gavin @ 19 January 2018

This is a thread to discuss the surface temperature records that were all released yesterday (Jan 18). There is far too much data-vizualization on this to link to, but feel free to do so in the comments. Bottom line? It’s still getting warmer.

[Update: the page of model/observational data comparisons has now been updated too.]

O Say can you See Ice…

Filed under: — gavin @ 6 November 2017

Some concerns about continued monitoring of sea ice by remote sensing were raised this week in Nature News an article in the (UK) Observer: Donald Trump accused of obstructing satellite research into climate change. The last headline is not really correct, but the underlying issues are real.

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1.5ºC: Geophysically impossible or not?

Filed under: — group @ 4 October 2017

Guest commentary by Ben Sanderson

Millar et al’s recent paper in Nature Geoscience has provoked a lot of lively discussion, with the authors of the original paper releasing a statement to clarify that their paper did not suggest that “action to reduce greenhouse gas emissions is no longer urgent“, rather that 1.5ºC (above the pre-industrial) is not “geophysically impossible”.

The range of post-2014 allowable emissions for a 66% chance of not passing 1.5ºC in Millar et al of 200-240GtC implies that the planet would exceed the threshold after 2030 at current emissions levels, compared with the AR5 analysis which would imply most likely exceedance before 2020. Assuming the Millar numbers are correct changes 1.5ºC from fantasy to merely very difficult.

But is this statement overconfident? Last week’s post on Realclimate raised a couple of issues which imply that both the choice of observational dataset and the chosen pre-industrial baseline period can influence the conclusion of how much warming the Earth has experienced to date. Here, I consider three aspects of the analysis – and assess how they influence the conclusions of the study.
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