All posts by Ed Hawkins

About Ed Hawkins

Climate scientist in the National Centre for Atmospheric Science (NCAS) at the University of Reading. IPCC AR5 Contributing Author. Can be found on twitter too: @ed_hawkins

Projected longer dry spells under climate change occur during dry seasons

The latest Intergovernmental Panel on Climate Change (IPCC) report states that the global water cycle will intensify with continued global warming. This means fewer rainy days, but with more intense rain over many land regions, and more variability generally. More dry days and longer dry spells have the potential to lead to negative impacts on crop yields and food security, as reductions in water availability limit crop growth. The impacts on crops also depend on the timing of these longer dry spells in the annual cycle and future delays in the wet season are also reported in the IPCC report and by my previous research.

Guest post by Caroline Wainwright
Continue reading Projected longer dry spells under climate change occur during dry seasons

Climate indicators

The recent IPCC AR6 WGI report summarises the state of knowledge of physical climate science, but the final version of the Summary for Policymakers (SPM) did not include a figure showing a range of indicators of our warming planet.

An earlier draft of the SPM included a figure like that below which aimed to put recent changes into a longer context of changes over the past 2000 years, and to show how other climate metrics have changed in recent decades. Many of these time series were shown in disparate places of the report, and have been brought together in this updated graphic which also indicates key milestones and discoveries in climate science.

Indicators (from top to bottom): atmospheric carbon dioxide concentration, ocean heat content, global sea level, global mean surface temperature, global lower tropospheric temperatures, Arctic sea ice amount, Kyoto cherry blossom date, specific humidity over land. Key moments in the history of climate science are indicated: the invention of the efficient steam engine by James Watt in 1790, the identification of the primary greenhouse gases by John Tyndall in 1861, the first estimate of climate sensitivity by Svante Arrhenius in 1896, and the discovery that the world was warming by Guy Callendar in 1938.

Continue reading Climate indicators

Adding observations to IPCC figures

The figures in the IPCC AR6 WGI SPM are a huge improvement over previous reports. However, one minor quibble is with the lack of observations shown. This brief post makes a figure available which is based on IPCC AR6 WGI SPM Figure 8, but with some observations added to show how global surface temperature and Arctic sea ice area have varied, compared to the model simulations. In my view this is a scientific improvement over the original version.
Continue reading Adding observations to IPCC figures

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.
Continue reading IPCC SPM Figures

The value of ‘data rescue’ for understanding record extremes

Record extreme temperature events are increasing in frequency as the climate warms. Several of these records have been surprising, in that they have been far above the previous record event for that location. Longer and earlier records, often possible through data recovery from undigitised archive material, would help quantify the risks of such record extreme temperature events. Continue reading The value of ‘data rescue’ for understanding record extremes

Storm Ulysses

On 27th February 1903 a major windstorm hit the UK and Ireland, known as Storm Ulysses.

The 20th Century Reanalysis (20CRv3) includes a modern reconstruction of the storm, created by assimilating available observations of surface pressure into a state-of-the-art weather forecast model.

There is a problem however. The number of available observations over north-west Europe is limited as most have never been digitised from the original hand-written paper sources. Recently, the WeatherRescue.org project rescued millions of observations, allowing us to examine the value of this new data by rerunning 20CRv3 with the new data added.
Continue reading Storm Ulysses

Warming patterns

Global warming does not mean the same amount of warming over the whole globe. There is a distinct spatial pattern to the long-term changes.

The first map below shows the total change in temperature since the early-industrial era, and the second map removes the global average warming to highlight regions of above and below average warming.

The largest warming is seen in the Arctic, and the land regions are clearly warming faster than the ocean. The striking blue area in the North Atlantic is a region of very little warming, and this is due to a decline in the strength of the Atlantic overturning circulation which brings warm water from the tropics to the northern latitudes.

All these features of the warming have been long predicted in climate model simulations, for example in IPCC AR4 and IPCC AR5.


Technical details: spatial pattern of warming uses approach described in Hawkins et al. (2020) using Berkeley Earth dataset, and the changes are relative to 1850-1900.