This blog post is a short summary of key points that are of current relevance to society from the physical science of climate change. It is based on the headline statements of a report published in 2021 by the Intergovernmental Panel on Climate Change (IPCC). The IPCC is a United Nations body responsible for providing impartial assessments of climate science. Its reports inform international negotiations on tackling climate change.
Written by Jonathan Gregory, Matt Palmer and Ed Hawkins
Continue reading Climate Change 2021 – the physical science basis
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.
Continue reading What would I say to COP26?
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.
Continue reading IPCC SPM Figures
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.
Continue reading Glimpsing the future
Recently, I was lucky enough to speak at an event at the Hay Festival – one of the most famous literary festivals in the world. The Festival had paired up three environmental scientists with three artists and authors to produce a series of hour-long live events, and provided us with an opportunity to talk about science with a very different audience. Continue reading Hay Festival
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
Just over a year ago I received an email from a colleague I had never met. Jan Fuglestvedt asked whether I had ever made a spiral version of my global temperature graphics. He ended by suggesting that this was ‘just a (crazy) thought’.
But, it was a Friday afternoon – what else was I going to do? Continue reading Spiral birthday
When designing scientific graphics, one key choice is about which colour scale to use (something discussed in several previous posts). The animated graphic below is a simulation of how an image would look to someone who is colour blind (a few percent of men). Continue reading Choose colour scales carefully