The following graphs, are something I put together to illustrate the scale of Climate Change, compared with historic temperatures we have experienced here, in England. I have used them in numerous presentations, and they feature in Reading’s first Adaptation Plan. For this update (January 2024), I have updated the CET data through to 2022, and I have created a number of annotated versions of the graph(s) to help guide the reader.
The Central England Temperature Record
In the description of the CET record, the Hadley Center met scientists note that “…These daily and monthly temperatures are representative of a roughly triangular area of the United Kingdom enclosed by Lancashire, London and Bristol…”. They also note that “…the monthly series, which begins in 1659, is the longest available instrumental record of temperature in the world…”, which makes it really interesting.
- The grey line shows the average annual temperature, for the Central England Area, from 1659 to 2022.
- The green, dashed-line is the trend of 30-year long-term averages (LTA)
- The black, dashed-lines (with arrows) shows three LTA periods: 1871-1900, 1961-90 and 1981-2020.
Adding the Climate Projections
Building on the previous graph…
- The dashed-lines (with arrows) show LTA periods: 1871-1900, 1961-90, 1981-2020, 2020-2049 and 2050-2079.
- The plume of rising temperatures – shaded from blue to red – show the range of model 30-year LTA results from the UK Climate Projections 2018 (UKCP18).
- Notice that the blue dashed-line is the 50-percentile average, assuming we limit Greenhouse Gas (GHG) emissions to meet the original 2°C Paris Climate Agreement target (RCP2.6).
- The red dashed-line is high emissions future average (RCP8.5), which could result as a combination of: high global economic growth or high population growth, with limited efforts to Mitigate fossil fuel emissions.
- Note that either future is considerably warmer than we have experienced in the whole CET record!
Developing the UKCP Climate Change ‘plume’
Adding the UKCP18 data to this is a powerful way of illustrating how climate change is going to make such a profound difference for us. I created a similar graph, using the previous 2009 climate projections (UKCP09) for my Extreme Events and Climate Change presentation. The latest climate projections offered the opportunity to create a more detailed graph, with an annual variation in the long-term average trends. I wanted to add a bit more scientific vigour by averaging temperature changes projected for the southern edge of the CET triangle (Reading was the obvious choice); with those from the northern apex (I chose Lancaster). The UKCP18 data is available in a similar form to the 2009 projections so extracting the data required similar thinking to what I worked through in the But what does it mean for me? section. You can see the result of the high emissions temperature plumes in the graph below. The warming in the south of the country is greater than in the north. At the 50 percentile level, it is nearly 1 deg C different by 2100. The simple average I generate for the final plot will be crude but, reasonable for the sake of this illustration…and certainly fair, given the uncertainty inherent in the climate projections anyway.
The low emission scenario data is developed in the same way. Note for this the north/south differences are smaller. Also for information on the scenarios, see the second section in this page. In the final graph, the low and high temperature plumes are blended, as they do overlap. Hence the final temperature plume is showing a certainty band where we are 90% sure that temperatures will be at least as warm as this, even in a low emissions future; and 90% sure that temperatures will not exceed the top of the plume, even in a high emissions future.
Updates to the graph
I put the first version of the CET + Climate Change graph together in 2012, for some presentations I gave to staff in the Environment Agency. I’ve tinkered with it since: to improve it as a communication tool; and to update the CET record, and the the Climate projections (from UKCP09 to UKCP18).
Updates to the UK Climate Projections
On 4 August 2022 the UK Climate Projections were updated. This included an update to the UKCP18 projections that I have used in the development of these graphs. However the report on the new modelling (see https://www.metoffice.gov.uk/pub/data/weather/uk/ukcp18/science-reports/UKCP18-Probabilistic-Update-Report.pdf from UKCP project news page) does note that changes to variables, like the mean annual temperature, that I have used, will be small.