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The global temperature jigsaw

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Since 1998 the global temperature has risen more slowly than before. Given the many explanations for colder temperatures discussed in the media and scientific literature (La Niña, heat uptake of the oceans, arctic data gap, etc.) one could jokingly ask why no new ice age is here yet. This fails to recognize, however, that the various ingredients are small and not simply additive. Here is a small overview and attempt to explain how the different pieces of the puzzle fit together.

AR5_temp_obs

Figure 1 The global near-surface temperatures (annual values at the top, decadal means at the bottom) in the three standard data sets HadCRUT4 (black), NOAA (orange) and NASA GISS (light blue). Graph: IPCC 2013. [Read more…] about The global temperature jigsaw

AGU 2013 preview and participation

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So, it’s that time of year again.

Fall AGU is the largest Earth Science conference on the planet, and is where you will get previews of new science results, get a sense of what other experts think about current topics, and indulge in the more social side of being a scientist. The full scientific program is available for searching here.

In recent years, there has been an increasing amount of virtual content – including live streaming of key sessions and high profile lectures, and continuous twitter commentary (follow the hashtag #AGU13), that give people not attending to get a sense of what’s going on. Gavin and Mike are attending and will try and give some highlights as the week goes along, here and via twitter (follow @ClimateOfGavin and @MichaelEMann).

Some obvious highlights (that will be live-streamed) are the Frontiers of Geophysics lecture from the Jim Hansen (Tuesday, 12:30pm PST), Senator Olympia Snowe (Monday, 12:30pm), Judith Lean (Tues 10:20am), the Charney Lecture from Lenny Smith (Tues 11:20am), James Elsner on tornado connections to climate change (Tues 2:40pm), David Grinspoon (the Sagan lecture, Thurs 9am), and Bill Ruddiman (Thursday 2:40pm). Some full sessions will also be livestreamed – for instance, The future of IPCC session (Tues 10:20am-12:30pm), and the Climate Literacy sessions (Tues 4:00pm-6:00pm, Wed 8am-12:30pm).

For attendees, there are a number of events close to our hearts: A bloggers forum for discussion on science blogging (Mon 5pm), the Open Mic night hosted by Richard Alley (Mon 7:30pm at Jillian’s Restaurant), and the AGU 5k run on Wednesday morning (6:30am).

Also AGU and the Climate Science Legal Defense Fund have organised a facility for individual consultations with a lawyer (by appointment via lawyer@climatesciencedefensefund.org) for people either who have found themselves involved in legal proceedings associated with their science or people who are just interested in what they might need to be prepared for. There is a brown bag lunch session on Friday (12:30pm PST) for a more informal discussion of relevant issues.

There are obviously many individual presentations that will be of interest, but too many to list here. Feel free to add suggestions in the comments and look out for updates all next week.

A failure in communicating the impact of new findings

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I was disappointed by the recent summary for policymakers (SPM) of the intergovernmental panel on climate change (IPCC) assessment report 5, now that I finally got around to read it. Not so much because of the science, but because the way it presented the science.

The report was written by top scientists, so what went wrong?

[Read more…] about A failure in communicating the impact of new findings

Unforced Variations: Dec 2013

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This month’s open thread. It’s coming to the end of the year and that means updates to the annual time series of observations and models relatively soon. Suggestions for what you’d like to see assessed are welcome… or any other climate science related topic.

Arctic and American Methane in Context

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Lots of interesting methane papers this week. In Nature Geoscience, Shakhova et al (2013) have published a substantial new study of the methane cycle on the Siberian continental margin of the Arctic Ocean. This paper will get a lot of attention, because it follows by a few months a paper from last summer, Whiteman et al (2013), which claimed a strong (and expensive) potential impact from Arctic methane on near-term climate evolution. That economic modeling study was based on an Arctic methane release scenario proposed in an earlier paper by Shakhova (2010). In PNAS, Miller et al (2013) find that the United States may be emitting 50-70% more methane than we thought. So where does this leave us?

[Read more…] about Arctic and American Methane in Context

References

  1. N. Shakhova, I. Semiletov, I. Leifer, V. Sergienko, A. Salyuk, D. Kosmach, D. Chernykh, C. Stubbs, D. Nicolsky, V. Tumskoy, and . Gustafsson, "Ebullition and storm-induced methane release from the East Siberian Arctic Shelf", Nature Geoscience, vol. 7, pp. 64-70, 2013. http://dx.doi.org/10.1038/NGEO2007
  2. G. Whiteman, C. Hope, and P. Wadhams, "Vast costs of Arctic change", Nature, vol. 499, pp. 401-403, 2013. http://dx.doi.org/10.1038/499401a
  3. N.E. Shakhova, V.A. Alekseev, and I.P. Semiletov, "Predicted methane emission on the East Siberian shelf", Doklady Earth Sciences, vol. 430, pp. 190-193, 2010. http://dx.doi.org/10.1134/S1028334X10020091
  4. S.M. Miller, S.C. Wofsy, A.M. Michalak, E.A. Kort, A.E. Andrews, S.C. Biraud, E.J. Dlugokencky, J. Eluszkiewicz, M.L. Fischer, G. Janssens-Maenhout, B.R. Miller, J.B. Miller, S.A. Montzka, T. Nehrkorn, and C. Sweeney, "Anthropogenic emissions of methane in the United States", Proceedings of the National Academy of Sciences, vol. 110, pp. 20018-20022, 2013. http://dx.doi.org/10.1073/pnas.1314392110

Sea-level rise: What the experts expect

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In the long run, sea-level rise will be one of the most serious consequences of global warming. But how fast will sea levels rise? Model simulations are still associated with considerable uncertainty – too complex and varied are the processes that contribute to the increase. A just-published survey of 90 sea-level experts from 18 countries now reveals what amount of sea-level rise the wider expert community expects. With successful, strong mitigation measures, the experts expect a likely rise of 40-60 cm in this century and 60-100 cm by the year 2300. With unmitigated warming, however, the likely range is 70-120 cm by 2100 and two to three meters by the year 2300.
[Read more…] about Sea-level rise: What the experts expect

Statistics and Climate

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Do different climate models give different results? And if so, why? The answer to these questions will increase our understanding of the climate models, and potentially the physical phenomena and processes present in the climate system.

We now have many different climate models, many different methods, and get a range of different results. They provide what we call ‘multi-model‘ and ‘multi-method‘ ensembles. But how do we make sense out of all this information?

[Read more…] about Statistics and Climate

Global Warming Since 1997 Underestimated by Half

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A new study by British and Canadian researchers shows that the global temperature rise of the past 15 years has been greatly underestimated. The reason is the data gaps in the weather station network, especially in the Arctic. If you fill these data gaps using satellite measurements, the warming trend is more than doubled in the widely used HadCRUT4 data, and the much-discussed “warming pause” has virtually disappeared. [Read more…] about Global Warming Since 1997 Underestimated by Half

Simple physics and climate

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No doubt, our climate system is complex and messy. Still, we can sometimes make some inferences about it based on well-known physical principles. Indeed, the beauty of physics is that a complex systems can be reduced into simple terms that can be quantified, and the essential aspects understood.

A recent paper by Sloan and Wolfendale (2013) provides an example where they derive a simple conceptual model of how the greenhouse effect works from first principles. They show the story behind the expression saying that a doubling in CO2 should increase the forcing by a factor of 1+log|2|/log|CO2|. I have a fondness for such simple conceptual models (e.g. I’ve made my own attempt posted at arXiv) because they provide a general picture of the essence – of course their precision is limited by their simplicity.

[Read more…] about Simple physics and climate

References

  1. T. Sloan, and A.W. Wolfendale, "Cosmic rays, solar activity and the climate", Environmental Research Letters, vol. 8, pp. 045022, 2013. http://dx.doi.org/10.1088/1748-9326/8/4/045022

Cows, Carbon and the Anthropocene: Commentary on Savory TED Video

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Guest post by Jason West and David Briske

Allan Savory delivered a highly publicized talk at a “Technology, Entertainment, Design (TED)” conference in February of this year (2013) entitled “How to fight desertification and reverse climate change.” Here we address one of the most dramatic claims made – that a specialized grazing method alone can reverse the current trajectory of increasing atmospheric CO2 and climate change.

The talk was attended by many conferees and has since been viewed on the TED website over 1.6 million times. It has received substantial acclaim in social media, some of which is available at the Savory Institute website, but it has also received considerable criticism (of particular note is a blog post from Adam Merberg and an article in Slate magazine. Although these criticism quickly followed Mr. Savory’s presentation and are broadly supported by the available science, his sweeping claims have continued to resonate with lay audiences. An apparent example is his invitation to deliver a speech to Swiss Re during their 150 year anniversary celebration in London in September, in which he is quoted as saying “…only now due largely to my TED talk on the desertification aspect of the global problem, was the public becoming aware of such hope in a world so short on solutions…”.
[Read more…] about Cows, Carbon and the Anthropocene: Commentary on Savory TED Video