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. Guest Commentary by Myles Allen A few weeks ago, I had an unusual — and challenging — assignment: providing a one-hour “tutorial” on the basic science of human-induced climate change to a Federal District Court in San

O Say Can You CO2…

Guest Commentary by Scott Denning The Orbiting Carbon Observatory (OCO-2) was launched in 2014 to make fine-scale measurements of the total column concentration of CO2 in the atmosphere. As luck would have it, the initial couple of years of data from OCO-2 documented a period with the fastest rate of CO2 increase ever measured, more than 3 ppm per year (Jacobson et al, 2016;Wang

1.5ºC: Geophysically impossible or not?

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 there 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

Sensible Questions on Climate Sensitivity

Guest Commentary by Cristian Proistosescu, Peter Huybers and Kyle Armour tl;dr  Two recent papers help bridge a seeming gap between estimates of climate sensitivity from models and from observations of the global energy budget. Recognizing that equilibrium climate sensitivity cannot be directly observed because Earth’s energy balance is a long way from equilibrium, the studies instead focus on what can be inferred about climate sensitivity from historical trends. Calculating a climate sensitivity from the simulations that is directly comparable with that observed shows both are consistent. Crucial questions remain, however, regarding how climate sensitivity will

Red team/Blue team Day 1

From Russell Seitz:

Unforced variations: July 2017

So, big news this week: The latest update to the RSS lower troposphere temperatures (Zeke at Carbon Brief, J. Climate paper) and, of course, more chatter about the red team/blue team concept. Comments?

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

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 islandâ€�, “cold parkâ€�, and diverse human induced

Don’t make a choice that your children will regret

Dear US voters, the world is holding its breath. The stakes are high in the upcoming US elections. At stake is a million times more than which email server one candidate used, or how another treated women. The future of humanity will be profoundly affected by your choice, for many generations to come. The coming four years is the last term during which a US government still has the chance, jointly with the rest of the world, to do what is needed to stop global warming well below 2°C and closer to 1.5°C, as was unanimously decided by 195 nations in the Paris Agreement last December. The total amount of carbon dioxide the world can still emit in order

Unforced variations: Aug 2016

Sorry for the low rate of posts this summer. Lots of offline life going on. 😉 Meantime, this paper by Hourdin et al on climate model tuning is very interesting and harks back to the FAQ we did on climate models a few years ago (Part I, Part II). Maybe it’s worth doing an update? Some of you might also have seen some of the discussion of record temperatures in the first half of 2016. The model-observation comparison including the estimates for 2016 are below: It seems like the hiatus hiatus will

Hiatus or Bye-atus?

Guest commentary by Stephan Lewandowsky, James Risbey and Naomi Oreskes The idea that global warming has “stopped” has long been a contrarian talking point. This framing has found entry into the scientific literature and there are now numerous articles that address a presumed recent “pause” or “hiatus” in global warming. Moreover, the “hiatus” also featured as an accepted fact in the latest IPCC report (AR5). Notwithstanding its widespread use in public and apparent acceptance in the scientific community, there are reasons to be skeptical of the existence of a “hiatus” or “pause” in global warming [Ed: see

And the winner is…

Remember the forecast of a temporary global cooling which made headlines around the world in 2008? We didn’t think it was reliable and offered a bet. The forecast period is now over: we were right, the forecast was not skillful. Back around 2007/8, two high-profile papers claimed to produce, for the first time, skilful predictions of decadal climate change, based on new techniques of ocean state initialization in climate models. Both papers made forecasts of the future evolution of global mean and regional temperatures. The first paper, Smith et al. (2007), predicted “that internal variability will

Ice-core dating corroborates tree ring chronologies

Guest commentary from Jonny McAneney You heard it here first… Back in February, we wrote a post suggesting that Greenland ice cores may have been incorrectly dated in prior to AD 1000. This was based on research by Baillie and McAneney (2015) which compared the spacing between frost ring events (physical scarring of living growth rings by prolonged sub-zero temperatures) in the bristlecone pine tree ring chronology, and spacing between prominent acids in a suite of ice cores from both Greenland

Global warming and unforced variability: Clarifications on recent Duke study

Guest Commentary from Patrick Brown and Wenhong Li, Duke University We recently published a study in Scientific Reports titled Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise. Our study seemed to generated a lot of interest and we have received many inquires regarding its findings. We were pleased with some of coverage of our study (e.g., here) but we were disappointed that some outlets published particularly misleading articles (e.g, here, here, and here). Since

The return of the iris effect?

Guest commentary from Andy Dessler (TAMU) When a new scientific hypothesis is published, two questions always occur to me: Did the authors convincingly show the hypothesis was correct? If not, is the hypothesis actually correct? The answers to these two questions may not be the same. A good example is Wegener’

The mystery of the offset chronologies: Tree rings and the volcanic record of the 1st millennium

Guest commentary by Jonny McAneney Volcanism can have an important impact on climate. When a large volcano erupts it can inject vast amounts of dust and sulphur compounds into the stratosphere, where they alter the radiation balance. While the suspended dust can temporarily block sunlight, the dominant effect in volcanic forcing is