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The 5th International Conference on Regional Climate

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The fifth international conference on regional climate (ICRC 2023), organised by World Climate Research Programme’s (WCRP) coordinated downscaling experiment (CORDEX), has just completed. It was a hybrid on-site/online conference with hubs in both Trieste/Italy (hosted by the International Centre on Theoretical Physics, ICTP) and Pune/India.

The hybrid set-up, with video links between the two hubs and digital attendence through zoom, was a change from previous ICRCs held in ICTP (2011), Brussels (2013), Stockholm (2016), and Beijing (2019). It worked impressively well, and the CORDEX ICRC 2023 streaming is available from the WCRP CORDEX YouTube channel.

It seems as an eternity since the previous ICRC before the COVID pandemic, so I was curious to see how things have progressed since then. It was also interesting to compare my impressions from this conference with my blog posts here on RealClimate from the first ICRC in Trieste, the second in Brussels, the third ICRC in Stockholm, I see that questions concerning uncertainty and added value are still being debated.

ICRC 2023
A panel discussion at the ICRC 2023 at ICTP
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Unforced variations: Oct 2023

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This month’s open thread on climate topics. Please try to stay on topic and refrain from posting tedious, oft-debunked nonsense. Look out for more reports of ridiculously high global temperatures and intense rainfall, and more confident predictions of the budding El Niño event and annual temperature rankings…

Old habits

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Media awareness about global warming and climate change has grown fairly steadily since 2004. My impression is that journalists today tend to possess a higher climate literacy than before. This increasing awareness and improved knowledge is encouraging, but there are also some common interpretations which could be more nuanced. Here are two examples, polar amplification and extreme rainfall.

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The Scafetta Saga

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It has taken 17 months to get a comment published pointing out the obvious errors in the Scafetta (2022) paper in GRL.

Back in March 2022, Nicola Scafetta published a short paper in Geophysical Research Letters (GRL) purporting to show through ‘advanced’ means that ‘all models with ECS > 3.0°C overestimate the observed global surface warming’ (as defined by ERA5). We (me, Gareth Jones and John Kennedy) wrote a note up within a couple of days pointing out how wrongheaded the reasoning was and how the results did not stand up to scrutiny.

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References

  1. N. Scafetta, "Advanced Testing of Low, Medium, and High ECS CMIP6 GCM Simulations Versus ERA5‐T2m", Geophysical Research Letters, vol. 49, 2022. http://dx.doi.org/10.1029/2022GL097716

As Soon as Possible

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The latest contrarian crowd pleaser from Soon et al (2023) is just the latest repetition of the old “it was the sun wot done it” trope[1] that Willie Soon and his colleagues have been pushing for decades. There is literally nothing new under the sun.

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References

  1. W. Soon, R. Connolly, M. Connolly, S. Akasofu, S. Baliunas, J. Berglund, A. Bianchini, W. Briggs, C. Butler, R. Cionco, M. Crok, A. Elias, V. Fedorov, F. Gervais, H. Harde, G. Henry, D. Hoyt, O. Humlum, D. Legates, A. Lupo, S. Maruyama, P. Moore, M. Ogurtsov, C. ÓhAiseadha, M. Oliveira, S. Park, S. Qiu, G. Quinn, N. Scafetta, J. Solheim, J. Steele, L. Szarka, H. Tanaka, M. Taylor, F. Vahrenholt, V. Velasco Herrera, and W. Zhang, "The Detection and Attribution of Northern Hemisphere Land Surface Warming (1850–2018) in Terms of Human and Natural Factors: Challenges of Inadequate Data", Climate, vol. 11, pp. 179, 2023. http://dx.doi.org/10.3390/cli11090179

Unforced variations: Sep 2023

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This month’s open thread on climate science topics. It’s been a warm summer, dontcha know? Expect ERA5, the satellite data and then the surface data products to confirm this in the next week or so. Sea ice minimum in the Arctic will also occur soon, as will a record low maximum in the Antarctic. El Niño still building in the tropical Pacific. Interesting times…

The AMOC: tipping this century, or not?

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A few weeks ago, a study by Copenhagen University researchers Peter and Susanne Ditlevsen concluded that the Atlantic Meridional Overturning Circulation (AMOC) is likely to pass a tipping point already this century, most probably around mid-century. Given the catastrophic consequences of an AMOC breakdown, the study made quite a few headlines but also met some skepticism. Now that the dust has settled, here some thoughts on the criticisms that have been raised about this study.

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What is happening in the Atlantic Ocean to the AMOC?

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For various reasons I’m motivated to provide an update on my current thinking regarding the slowdown and tipping point of the Atlantic Meridional Overturning Circulation (AMOC). I attended a two-day AMOC session at the IUGG Conference the week before last, there’s been interesting new papers, and in the light of that I have been changing my views somewhat. Here’s ten points, starting from the very basics, so you can easily jump to the aspects that interest you.

Figure 1. A very rough schematic of the AMOC: warm northward flow near the surface, deep-water formation, deep southward return flow in 2000 – 3000 meters depth. In the background the observed sea surface temperature (SST) trend since 1993 from the Copernicus satellite service, showing the ‘cold blob’ in the northern Atlantic west of the British Isles discussed below. Graph by Ruijian Gou.
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Area-based global hydro-climatological indicators

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The World Meteorological Organisation (WMO) Global Climate Observing System (GCOS) and Copernicus Climate Change Services (C3S) both provide sets of global climate statistics to summarise the state of Earth’s climate. They are indeed valuable indicators for the global or regional mean temperature, greenhouse gas concentrations, both ice volume and area, ocean heat, acidification, and the global sea level.

Still, I find it surprising that the set does not include any statistics on the global hydrological cycle, relevant to rainfall patterns and droughts. Two obvious global hydro-climatological indicators are the total mass of water falling on Earth’s surface each day P and the fraction of Earth’s surface area on which it falls Ap.  

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