Category Archives: communication

What would I say to COP26?

The recent 6th Assessment Report of Working Group I of the Intergovernmental Panel on Climate Change (IPCC) is the result of years of diligent assessment of the latest scientific evidence on climate change building on several previous similar assessments. It was written by hundreds of authors, and openly reviewed by thousands of experts. Every word of the Summary for Policymakers was agreed by all 195 parties to the UNFCCC and at COP26.

The report is clear that the world has warmed by around 1.1°C since the industrial revolution, and that this is due to human activities, primarily burning fossil fuels. As a direct consequence, heatwaves and heavy rainfall events have become more frequent and more intense. As the oceans have warmed and the ice sheets have melted, sea levels have risen, increasing the risk of coastal flooding. Our past greenhouse gas emissions have caused changes of the climate which have harmed both human society and ecosystems.

We are at a crossroads.

The global choices being made now determine what happens to the climate next.
Continue reading What would I say to COP26?

IPCC SPM Figures

The Working Group I (WGI) component of the IPCC 6th Assessment Report (AR6) has been released. One key development since AR5 was the involvement of professional graphic designers in creating the figures for the Summary for Policymakers (SPM). As a result, the graphics are clear and usable, having been user-tested through several design iterations. The data underlying the figures are also openly available.
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Glimpsing the future

In December 2019, the average temperature across Australia was about 2°C above what would be expected for the present-day, which is another 1.5°C above temperatures that were normal for December before humans started warming the climate. These extreme temperatures have contributed to the catastrophic bushfires which have devastated large areas.

But what may be considered ‘normal’ is constantly changing.

In a world which has warmed by 3°C – roughly the current global trajectory – what was extreme will be entirely normal.


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Uncertainty in warming since pre-industrial times

The consequences of the Paris Agreement’s choice of the pre-industrial as its baseline have been discussed previously on this blog. This choice makes sense from a climate forcing perspective (as radiative forcings are measured with respect to a quasi-equilibrated state, and the well-observed recent past is not close to have finished responding to anthropogenic drivers). Looking back into the pre-industrial period, there are fewer instrumental observations of the temperature across the globe. So naturally our knowledge of the pre-industrial baseline temperature is uncertain.

Recent work, such as Hawkins et al. (2017) and Schurer et al. (2017), have looked to assess and quantify this uncertainty in light of future targets. The magnitude of this uncertainty, although small, becomes important when you consider the amount of warming left between today and the 1.5°C target. Continue reading Uncertainty in warming since pre-industrial times

Letter to Lamar Smith

The Committee on Science, Space & Technology of the US House of Representatives conducts regular evidence hearings on various science topics. On Wednesday 29th March, there is a hearing on “Climate science: assumptions, policy implications, and the scientific method”. The following letter, summarising the scientific findings of Fyfe et al. (2016) and Karl et al. (2015), has been submitted as evidence to this hearing.

The broader context is that the Committee Chairman, Mr. Lamar Smith, has previously discussed the findings of Fyfe et al. (of which I was a co-author), claiming: “A new peer-reviewed study, published in the journal Nature, confirms the halt in global warming”. This statement is incorrect, and motivated the clarification on what Fyfe et al. actually says.

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