Revealed: The 11 slides that finally convinced Boris Johnson about global warming

A scientific briefing that UK prime minister Boris Johnson says changed his mind about global warming has been made public for the first time, following a freedom-of-information (FOI) request by Carbon Brief.

Last year, on the eve of the UK hosting COP26 in Glasgow, Johnson described tackling climate change as the country’s “number one international priority”. He also published a net-zero strategy and told other countries at the UN General Assembly to “grow up” when it comes to global warming.

However, just a few years earlier, Johnson was publicly doubting established climate science. For example, in a Daily Telegraph column published in 2015 he claimed unusual winter heat had “nothing to do with global warming”. And, in 2013, he said he had an “open mind” to the idea that the Earth was heading for a mini ice-age.

Last year, acknowledging his past climate scepticism, Johnson told journalists that he had now changed his mind, largely due to a scientific briefing he received shortly after becoming prime minister in 2019.

Johnson admitted he had been on a “road to Damascus” when it comes to climate science:

“I got them [government scientists] to run through it all and, if you look at the almost vertical kink upward in the temperature graph, the anthropogenic climate change, it’s very hard to dispute. That was a very important moment for me.”

The Sunday Times later reported that this briefing had been given by Sir Patrick Vallance, the government’s chief scientific advisor, and, according to one of the prime minister’s close allies, it “had a huge impact”.

Using a FOI request submitted to the UK’s Government Office for Science (“GO-Science”), Carbon Brief has now obtained the contents of this pivotal scientific briefing, which took place on 28 January 2020 inside 10 Downing Street.

Below, Carbon Brief reveals the 11 slides that were used to “teach” Johnson about climate change, as well as the email correspondence exchanged between leading scientists and advisors as they prepared the prime minister’s briefing.

[Jump straight to see the 11 slides used in the presentation.]

The emails suggest that some No 10 advisors were suspicious of important aspects of climate science – for example, asking whether UN’s Intergovernmental Panel on Climate Change (IPCC) reports were “worth taking note of”.

Email correspondence

The exchange of emails begins on 23 January 2020 when someone in the office of the  government’s chief scientific adviser, Sir Patrick Vallance, emails Met Office chief scientist Prof Stephen Belcher and Prof Gideon Henderson, the chief scientific adviser at the Department of Environment, Food and Rural Affairs (Defra).

(See Carbon Brief’s in-depth interview with Belcher published in April 2018.)

The message describes plans for a climate change-themed “teach in” involving the two scientists which will be attended by a selection of No 10 staff, including some redacted names and “SpAds” (special advisors). Munira Mirza has been the director of the “No10 policy unit”, which is referred to in the email, since Johnson became prime minister in 2019. (See the note at the end of the article about the reasoning given by GO-Science for redacting some names.)

Also copied into the email is Dr Stuart Wainwright, who is the director of GO-Science and, therefore, works under Vallance.

Henderson responds, noting that “we’ll need to prioritise this when we hear the time”.

The next day, an email is sent “on behalf of” Dominic Cummings, then the prime minister’s chief adviser, inviting the scientists to an event on 28 January in the Cabinet Room at No 10.

Shortly afterwards, Wainwright contacts Belcher outlining what they want to cover in the briefing. The plan focuses on what could be described as the basics of climate science, including evidence for human-caused climate change and the formation of scientific consensus. There is a notable focus on “uncertainty”. 

This is followed by an email from Vallance’s office to a number of people, including Cummings, reiterating these three priority areas and indicating that Belcher has “previously discussed an idea of how to structure the session” with the chief scientific adviser. 

They indicate that Belcher should “liaise with academic colleagues on pulling something together”, to which he replies: “Will do.” (The Met Office has confirmed to Carbon Brief that its senior climate scientists Prof Richard Betts and Prof Peter Stott both assisted Belcher in preparing for the briefing.)

An email from Wainwright follows explaining that the planned climate change session is “part of a broader set of teach in’s [sic] on various policy, economic, science aspects that will inform advice to the PM”. 

At this point, Johnson had been in No 10 for six months, after taking over as Conservative leader in July 2019 and winning a general election in December.

The next email is from Chris Pook, a deputy director in GO-Science working under Wainwright and Vallance. 

He invites Richard Barker, head of energy and environment at National Physical Laboratory, to participate in the meeting as an expert, saying they need someone who can discuss uncertainty in climate measurements and help understand “what this means for decision-making”. 

Two days later, on 26 January, Belcher emails the government scientists explaining that he has been working on a series of slides. Topics he mentions include the “need for quantitative advice on carbon budgets to achieve targets” and “current challenges” on tipping points and future impacts and extremes. 

He also says they could discuss the concept of scientific peer review, the Intergovernmental Panel on Climate Change (IPCC) and Berkeley Earth, a US-based institution that analyses land temperature data, “as an example of a new group coming in as independent tests”.

Additionally, he suggests a selection of five experts who could contribute to the session. The names of all but one – Baroness Brown, chair of the Climate Change Committee’s (CCC) adaptation committee – are redacted. One is proposed with the caveat that “she has done lots of media work, quite campaigning”. Another is described as an “excellent communicator on impacts”. A further suggestion comes with the remark: “I appreciate Stuart you thought she might appear too close? She is excellent.”

On 27 January, the day before the meeting, Vallance’s office contacts Belcher confirming that Barker and another individual whose name has been redacted will be invited to the event. They mention that they have been delayed due to “trying to juggle the response to Wuhan coronavirus”. (The first cases of Covid-19 in the UK were confirmed four days later.)

This email builds on the three priority areas previously mentioned, adding some more specific questions that No 10 would like the experts to address. These questions indicate a degree of scepticism about some of the key processes underlying climate science:

“No10 will want an answer to the question ‘why are the numbers so round’ eg 2050 target, and 1.5 degree etc. They also mentioned the IPCC reports and authors – ‘scientists or not’ – and are the reports worth taking note off!!! [sic]”

The “2050 target” likely refers to the UK’s legally binding goal for achieving net-zero emissions by 2050, established during the final days in office of Johnson’s predecessor, Theresa May. The mention of “1.5 degree” references the Paris Agreement’s stretch goal of limiting warming to 1.5C, which scientists think would limit some of the worst impacts of climate change.

The IPCC is a UN body that is regarded internationally as the authority on climate change. Its landmark assessment reports, assembled by hundreds of leading scientists every seven years or so, present comprehensive overviews of the state of knowledge on the topic.

This email is followed later that day by an internal message between GO-Science staff indicating that Belcher will lead the session and reiterating some key points from the session plan.

Again, this message highlights a focus on “what’s clear, what’s unsettled”, how scientific consensus is reached, “convenient numbers” and whether the IPCC process is “actually science”. 

It also asks: “…should we be worried that [the] range of uncertainty hasn’t changed (climate sensitivities)?” This references the point that estimates of climate sensitivity – a measure of how much the planet is expected to warm in response to rising CO2 levels – had not been narrowed for decades. While this is no longer the case following new research captured in last year’s IPCC sixth assessment report (AR6), this information had not yet been published at the time.

The final line of the email mentions a “Koonin red-teaming exercise” – presumably a reference to Dr Steven Koonin, a US physicist who has worked for both BP and the Obama administration, and who has more recently been accused of downplaying the severity of climate change.

During the years of the Trump administration in the US, Koonin advocated for a “red team” methodology to “test assumptions and analyses, identify risks, and reduce – or at least understand – uncertainties” around climate science. The approach saw some support within the Trump administration, but was dismissed by other scientists as inappropriate for assessing climate science. No such exercise ever ended up taking place.

It is notable that Dominic Cummings has also been a prominent supporter of the “red-team” approach in various fields as a means of combating what he describes as “groupthink and normal cognitive biases”. (Carbon Brief has approached Cummings for comment, but, upon publication, had not received a response.)

As the meeting approaches, the participants arrange a 45-minute “pre-meet” before heading to No 10. At this point, Belcher, Henderson, Vallance and Barker are listed as attending the meeting, along with one more redacted name. Another redacted name is unable to come as “she is in France”.

On the morning of 28 January, Belcher sends over his slides – which he describes as “reasonably vanilla” – to “guide discussion later today”. Among other things, he emphasises that the “goal is to stabilise climate, which requires net-zero emissions”. He asks for feedback from the others.

Henderson responds with some last-minute changes to the presentation. He notes that it largely misses out impacts of sea-level rise, including on the UK and its flood defences, something that is “perhaps more important than arctic [sic] sea ice for HMG [the government]”.

He adds that, “personally, I would put more focus on C cycle [carbon cycle] as cause of problem, important feedbacks, and the bit we need to act on”.

There is another, lengthy, response to Belcher from a redacted email address. It suggests adding a chart showing the long-term record of carbon dioxide (CO2), as well as various climate impacts taken from the IPCC, including huge losses for coral reefs, impacts on crop production and increased spread of various diseases. The writer stresses that “it may be worth pointing out that to achieve 1.5C (and perhaps 2C) requires net *negative* emissions”.

They also attach the chart below as an example of one that could be added to the presentation, noting that a “striking thing to show” would be “the long-term record of CO2”. They note that they cannot find a suitable chart from the IPCC’s fifth assessment report (AR5), published in 2013, and so include one from the fourth assessment (AR4), from 2007. The emailer notes that “it’s out of date, of course – CO2 is now up to 400 ppm [parts per million]”.

The chart, or a more recent version of it, does not make it into the final presentation.

Barker also responds to Belcher’s call for suggestions with a “rather basic question” around the conclusion they want to present to No 10:

“My assumption is that we want this meeting to establish the big opportunity for us to take a big step forward.”

While Belcher says he will leave Vallance to “comment on the overall purpose of the meeting”, there is no email from the chief scientific adviser clarifying this point in the released documents. His office does note again at this point that they are “currently quite immersed in coronavirus”.

Finally, as the meeting approaches, the final slides are sent out to GO-Science with a request for 15 hard copies to be printed, possibly indicating the final number of attendees at the event.

(Carbon Brief has learned that Boris Johnson received at least one further science briefing on climate change following this January 2020 presentation. In March 2021, for example, he was specifically briefed about, among other topics, the projected climate impacts at 2C and 4C of global warming. The information about these impacts was prepared by Prof Richard Betts from the Met Office and the University of Exeter using findings from the EU-funded HELIX project. Prof Betts also provided UK examples from the Technical Report of the Third UK Climate Change Risk Assessment, often known as CCRA3. Carbon Brief also understands that, even though Sir Patrick Vallance led the briefing at No 10 Downing Street on 28 January 2020, the 11 slides themselves were presented by Prof Belcher.)

Science slides

Below, with explanation by Carbon Brief, are the 11 slides shown to the prime minister on the evening of 28 January 2020 in the Cabinet Room at No 10 Downing Street.

Slideshow by Tom Prater for Carbon Brief

All 38 emails released under the Freedom of Information Act 2000 by GO-Science to Carbon Brief can be viewed as a PDF. An earlier version of the presentation, which was discussed and shared in the emails, can also be viewed as a PDF, as well as the final version shown to the prime minister, also available as a PDF.

In responding to Carbon Brief’s FOI request, GO-Science provided the following explanation for why it delayed the release for more than a month to conduct a “public interest” test, as well as why some names in the emails were redacted:

“The requested information engaged Section 35(1)(a) – information related to the formulation of government policy; because of this we have carried out a public interest test. In this instance the information is in relation to factual background information and scientific consensus on climate science, provided to inform policy decisions regarding climate change. There is a high public interest in climate change-related policies, which have and will have a significant impact on the public. Given the public interest in transparency regarding the scientific information provided to government in this context, we have determined that it is in the public interest to disclose the information held, and we have not applied this exemption. We are refusing some of this information (redacted in the annexes) under: Section 40(2) – Personal information. We have withheld personal information if disclosure would breach one or more of the principles of the UK General Data Protection Regulation (UK GDPR) or Data Protection Act 2018.

Carbon Brief also submitted an FOI request to the Cabinet Office asking for the same information about the 28 January 2020 briefing, but it responded – inaccurately, as GO-Science’s release of files proves – saying: “Searches of our records have not identified any information in scope of your request under the Act.”