Carbon Brief: Let’s start with an easy one, as it were. Your academic career started with astronomy and physics. How did you come to take the turn into atmospheric sciences?

Katharine Hayhoe: My undergraduate degree is in astronomy and physics, and I was happily anticipating a graduate career studying galaxy clustering around quasars, which is what was the subject of my undergraduate research, when to finish my degree I had to take one other course. I had already taken a minor in Spanish. I had already taken the [laughs] Gothic cathedral and children’s literature, so when I was looking around for an extra course that might be interesting and I saw a class on climate modelling over in the geography department. I thought to myself, “Well, that’s probably interesting, but probably easy. Why don’t I just take it?”

I didn’t take it out of any curiosity as to whether climate change was real or not, because growing up in Canada – you know – the grass is green, the sky is blue, climate is changing due to human activities. That’s kind of the factual way in which it’s presented. But what I did not realise until I took that class was, first of all, that climate modelling is all the very same physics that you learn in astrophysics – it’s essentially a special case of planetary atmospheres, it depends on radiative transfer and nonlinear fluid dynamics – so it was the exact same things I had already been studying.

And then, the second thing I learned was that climate change is such an urgent problem – because up until that point I viewed climate change as one of a suite of important environmental problems: air pollution, water pollution, biodiversity loss, climate change. But I did not realise that climate change is, as the military now puts it, a “threat multiplier” that is exacerbating all of those other issues to the point where we are not going to be able to fix any of those other issues if we leave climate change out of the picture. Not only that, but climate change is exacerbating humanitarian issues, as well – hunger, poverty, lack of access to clean water – it’s exacerbating these, too.

And so, I realised then that I serendipitously had the exact skill set that you need to do this work, and I realised that this was really an incredibly important and urgent issue. So I thought to myself, “Well, maybe I will work on this. I’ll go to graduate school and I’ll work on this until we fix it. Because it’s so urgent, surely we’ll fix it soon. And then I’ll go back to astrophysics.” That was a very long time ago.

CB: And now a lot of your work seems to focus a lot on the local and regional impacts of climate change. How reliable are the scientific methods for generating projections of that kind of scale – the local and the regional – do scientists have all the tools they need?

KH: That is exactly the question that my research addresses. I evaluate global climate models to see if they have the right large-scale weather patterns in them to accurately and correctly simulate things like drought, heavy rainfall events, cold or hot events, at the local scale. Depending on what region of the world you’re looking at and depending on what question you’re asking, sometimes the answer is yes and sometimes the answer is no. And then what I do is I evaluate the downscaling methods we use to take the relatively coarse information from the big global models and downscale it to much higher spatial and sometimes even high temporal resolution at the local to regional scale. The type of information that water managers or city planners or even health experts need to prepare for how climate is changing.

So I evaluate these downscaling methods to figure out which ones are capable of doing what. Some of them are great for looking at annual and seasonal averages, but they’re not so good when you start to look at day-to-day extreme values. Some are excellent on temperature, but they’re not so great on precipitation. I also develop new ones, too, because when I learn the problems that we have with the existing ones, of course it makes me want to develop something better.

And then, I work with people on the ground who want this information to put into water management models, to put into crop yield models, to put into models of how humans respond to extreme heat conditions and what impact that would have on our health. It fascinates me because we’re actually putting this information to practical use to help real people, and that’s why I decided to study climate change.

CB: On climate modelling, what do you think are the main priorities for improving models in the near term – in the next decade?

KH: That’s a great question. Climate modelling is an enormous undertaking. I think few people realise just how complex these models are. As soon as there’s a new supercomputer available anywhere in the world, there’s a climate model waiting to be run on it because we know that many of our physical processes right now are not being directly represented. They have to be “parameterised” because they occur at spatial or time scales that are smaller than the grids in the time steps that we use. So the smaller the spatial grids and the smaller the time step we use in the model, the better we’re able to actually explicitly resolve the physical processes in the climate. But, of course, that’s very expensive in terms of computational time.

We’re also learning that natural variability is really important when we’re looking over time scales of anywhere from the next year or two to even a couple of decades in the future. Natural variability is primarily controlled by exchange of heat between the ocean and the atmosphere, but it is an extremely complex process and if we want to develop better near-term predictive skills – which is looking not at what’s going to happen in the next three months but what’s going to happen between the next year and 10 years or 20 years or so – if we want to expand our understanding there, we have to understand natural variability better than we do today.

Also, climate models started off by being designed by physicists, so the very first climate models had nonlinear fluid dynamics in them and radiative transfer – that was all. Then they introduced sea ice and the land surface, clouds, some chemistry, some biosphere biology, but our land surface models are still fairly rudimentary compared to the other parts of the model. Other parts of the model are much more sophisticated because they were originally developed by people who had experience in oceanography and atmospheric science. We are just starting to understand, from a scientific perspective the enormous role that the soils play in responding to changes in climate, as well as changes in the carbon budget.

And so, I think some of the enormous advances that we are going to see in the next few years and even decades of climate models is incorporating other aspects of the climate system that are not purely just the ocean and the atmosphere.

CB: What do you think are the biggest unknowns that remain about future climate change? What are the biggest surprises? And where are they likely to come from?

KH: We recently published a climate science report for the US federal government. The Climate Science Special Report is volume one of the fourth US National Climate Assessment. The irony is inescapable that this report was published just before COP23 in Bonn where the US is the only country in the world who is planning to pull out of the Paris Agreement. That country has the most up-to-date science report in the entire world, because of course the IPCC [Intergovernmental Panel on Climate Change’s most recent assessment report] is about five years old now and the new one isn’t coming until after 2020.

In this climate science report, my favourite chapter – if you can call it that when it’s actually kind of scary – is the last chapter where we talk about the potential for surprise. We talk about the “known unknowns” – the things we know we don’t know. We talk about the “unknown unknowns” – the things we don’t even know that we don’t know, but we know that they’re out there. And we talk about how climate models systematically underestimate the magnitude of palaeoclimate warming, which suggests there are processes in the climate system that operate over longer time scales – because when we see climate changes happening in the past, we typically see the full reaction of the Earth system not over decades, but over hundreds and even thousands of years. But it suggests that there are long-term processes in the climate system that we’re not yet incorporating in our models and when we do, the final outcome of this inadvertent experiment that we’ve been conducting with our planet is likely to be worse, not better, than we thought

CB: It’s not possible to talk to a climate scientist – particularly one from North America – without mentioning Donald Trump. How do you think his election has affected the climate change conversation in the US and globally?

KH: Today, in the US, the number one predictor of what someone thinks about climate science – whether it’s real, whether humans are responsible, whether the impacts are serious – has nothing to do with how much we know about the science and everything to do with where we fall on the political spectrum. One of the biggest differences over all issues between Republicans and Democrats today in the United States is over whether or not they agree with the science of climate change. But something very interesting happened when Trump was elected.

So often we think that the most dangerous myth that the most people in the US have bought into is the myth that humans aren’t responsible for climate change, that this thing isn’t real. It’s true, there are many people that think that. But, if you look at the Yale climate opinion map, you’ll see that there are several maps that are substantially more negative than whether you think climate is changing and humans are responsible. The much more negative maps are do you think climate will affect you personally? Nobody thinks it will. And do you ever talk about it or hear somebody else talk about it? No. So the problem we were confronting was the fact that everybody thought, “If it really gets bad, someone else will fix it. I don’t think it’s bad right now. I don’t think it’s affecting me. Someone else will fix it.” Well, guess what? No one else is going to fix it now.

And so, after he has been elected, I have heard more conversations about climate change. Groups that I know, like Citizens Climate Lobby, for example, have had so many more people sign up to join the organisation. I have had so many people email me personally saying, “What can I do? I need to do something? I thought someone else would take care of it for me, but now I know they won’t. What can I do?” And strangely – I know this sounds very strange – but I really believe that his election galvanised people into personal action in a way that never would have happened if [Hilary] Clinton had been elected. I mean, just take, for example, the fact that there’s this “We’re Still In” movement. The We’re Still In movement consists of cities, states, business and investors that represent 30% of the US economy and 40% of its population. They are committed to meeting the Paris Agreement. And here’s the interesting thing: I think they have a better chance of actually doing it than the entire country under watered-down policies, like the clean power plan, that were not sufficient to get all the way there, and were such a tough sell to get anyone in the federal government to agree to anything. It’s much easier to get agreement at the state and the city level, as well as in a business. And interestingly, I feel like we may be further along because of these four years than if we had felt someone else was going to take care of it. I’m not sure and I wait to see, but there are indications.

CB: Interesting that you mention about the city and state level. In the New York Times recently, Michael Bloomberg and Jerry Brown wrote about Trump’s “abdication of leadership”, as they put it, on climate change at the federal level. They said there’s a risk that non-federal actions – at the city and the state level – could go unrecognised by the global community when they look at the US. Do you see that as a risk?

KH: I do because the UNFCCC [United Nations Framework Convention on Climate Change] framework – the process – was set up to work exclusively with nations. It was not set up to partner with cities or with states, despite the fact that California, for example, is one of the Top 10 economies in the world all by itself. Today, cities are the incubator of change. That is where much our change is happening. Because of their population density, they are both uniquely vulnerable to a changing climate, but they are uniquely able to instigate mitigation programmes and advances that you can’t do in less densely populated areas. So the very people and the very places where much of the change is happening or the potential for change is greatest are, by definition, excluded from the COP negotiations.

CB: On a similar note, on a federal level, what’s your view of [US Environmental Protection Agency administrator] Scott Pruitt’s red team/blue team approach to reviewing the science of climate change?

KH: Right. A thermometer isn’t Democrat or Republican. It doesn’t give you a different answer depending on how you vote. The only time it gives you a different answer is if you pretend it does. I think that it’s been clearly demonstrated that if such a blue team/red team debate occurred, it would not occur in good faith. It would occur with truth on one side and with fabrication and falsehood on the other, because the only way you can get a thermometer to tell you it isn’t warming is to lie about it.

The American Institute of Physics, I believe – you’ll have to check on this [it was actually the American Physical Society] – but I believe the American Institute of Physics actually did a red team/blue team exercise a number of years ago. [Physicist and New York University professor] Steve Koonin was involved in it – the very person who was involved in calling for this red team/blue team. As far as I can tell, nothing came of it. It didn’t work. Because a red team/blue team approach is only valid when all of the actors are participating in good faith.

I would say one more thing, too. One of the most important things that people need to know is the fact that there’s not a 50-50 debate on this. Scientists agree. When you ask the public what proportion of scientists agree, they say it’s about 50-50. Why? Because every time they turn on the TV, there’s one head saying it’s a catastrophe and there’s another head saying it’s a complete fabrication. Or sometimes the TVs will get a bit fancy, you’ll have six heads arguing over whether it’s real or not. Of course people don’t think that we agree on it, but we do.

And so, when we engage in a 50-50 debate, we are perpetuating the myth that this up for discussion, this is under debate, that we’re not quite sure and there are very valid points on both sides of the fence as to whether climate is changing and whether humans are responsible. Now, don’t get me wrong, there is plenty of room for debate in climate science. Plenty. I have been at many very interesting scientific meetings where people are disagreeing over what’s happening to the frequency of hurricanes, or what’s the best parametrisation method to use for cloud particles in global models, or what’s the role of natural variability versus human forcing at the regional scale. There’s plenty of debates – genuine debates – in the climate science field, but there is no legitimate debate over whether climate is changing and humans are responsible because, as the Climate Science Special Report says, there is no alternative explanation for the warming.

If you look at natural factors, every single natural factor either says there will be no change or we should actually be cooling right now. If we look at the sun, if we look at volcanoes, if we look at orbital forcing, and if we look at natural cycles, none of them can explain the warming. In fact, we should actually be getting cooler today.

CB: You mentioned before about a US withdrawal from the Paris Agreement. What impact do you think that would have? For example, what do you think it would affect the chances of limiting warming to 1.5C?

KH: That’s a good question. It’s challenging and it’s difficult and it’s discouraging when one of the largest emitters in the world – and historically, if you look at cumulative emissions, the largest emitter in the world – decides that somehow they live on a different planet, that what everybody else does doesn’t matter to them and vice versa. They’re deciding that, figuratively, they can build walls all up to the stratosphere and beyond and somehow just separate off their country from the rest of the world. That’s not the way the world works.

And so, by the United States refusing to participate in an agreement, which it helped negotiate, it’s like giving the world the finger – saying, “I don’t want to be part of you.” Well, the technology is not yet there to detach a country and put it into its own separate orbit. The reality is that we are all intimately connected, not just by the air that we breathe, not just by the water that we drink, but we also are connected by our flow of money and goods and resources across almost every boundary in the world. So, from that perspective, it’s discouraging. But, from the perspective of what will it take to meet the Paris Agreement, the fact that the US announced it will be withdrawing from the Paris Agreement – and of course it could always rejoin with a future administration – but the fact that the US announced that it was going to withdraw actually made many others step up to the plate.

CB: The topic on 1.5C, do you think it’s possible to meet that limit without negative emissions technologies and/or geoengineering. Are they our big hope, a necessary evil or to be avoided at all costs?

KH: Can we meet the 1.5C target? It is still technically possible, but if we continue on our current emission rates for more than a decade or so, we will not be able to meet 1.5C without substantial deployment of technology to remove CO2 from the atmosphere. I’m not familiar enough with that technology to tell you if we can do it a cost effective way. I know it’s out there. There’s amazing things like artificial trees and a negative emissions power plant in Iceland that is actually producing blocks of stone made out of CO2. The resources are there; the technology is there. But it is currently quite expensive to suck that CO2 out of the air to turn it into a useful product. But if we are going to meet that 1.5C goal and if we don’t see very serious action almost immediately, that type of technology is going to have to be deployed at a very broad scale producing net negative emissions well before the end of the century in order to keep us below 1.5C.

Now, one of the other technologies that has been proposed is solar radiation management, which is a type of geoengineering. Now, geoengineering is not chemtrails– that’s a conspiracy theory. Geoengineering can be as simple as tree planting because trees suck CO2 out of the atmosphere. But geoengineering can also be extremely high tech, like the idea of mimicking a volcanic eruption. A volcanic eruption spews enormous amounts of soot and dust into the atmosphere, and if it’s high enough up in the stratosphere, that soot and dust can circle the world for a year or more. It acts like a reflective blanket or an umbrella reflecting the energy of the sun back to space, which cools the Earth off. Some are proposing this as a possible solution to climate change, and ironically some of the very same US politicians who have persecuted climate scientists for peer review publications stating that “Yes, the Earth is warming”, they’re exploring the potential of geoengineering. Why would you explore geoengineering if you don’t think the planet is warming? It just illustrates the massive logical disconnect that we see in Washington today.

Would geoengineering work? Yes. The idea of brightening marine clouds through introducing little particles that would act as cloud condensation nuclei. The idea of putting soot and dust way up in the atmosphere where it would reflect the sun’s radiation. Those ideas could effectively limit global temperature. But there’s a couple of big “buts”.

Number one, as soon as they stopped, the temperature would shoot right back up to where it would be otherwise, and that type of abrupt change can be devastating. If you do decide to do something like that, you have to commit to it for a very long time because if you stopped, things could be just as bad or even possibly worse than they would have been without it.

Number two, they limit the temperature rise, but they don’t affect other things like all the CO2 that’s going into the ocean causing ocean acidification, and some of the changes in atmospheric circulation patterns that affect precipitation and drought.

And then, third, it would be conducting an experiment with the entire planet – deliberately – that has never actually been done before. It would be like giving an experimental drug to every single person on the planet on the same day without fully knowing what all the side effects are. And the one thing we know is that there’s always something we don’t know.

So I support small-scale experiments such as are being proposed to study what we don’t know about geoengineering. I support modelling studies of geoengineering. I think we need to know everything we possibly we can about this thing, because my fear is that someone will go ahead and do it before we know what the full impacts are, and we need to understand what those are and if there’s things that we didn’t expect that would cause tremendous impacts. For example, all the solar radiation that would be reflected back to space, what impact might that have on crop yields? Could it cause widespread famine as has occurred in the past after big volcanic eruptions, such as [Mount] Tambora. We need to know this before – long before – we put geoengineering on the table as a viable option

CB: On a slight change of tack, we’re at All Souls Church in Langham Place and you’re due to speak on climate change and faith. Do you think that faith is more likely to be a catalyst or a barrier when it comes to being concerned about climate change?

KH: Faith is often perceived to be a barrier when it comes to caring about a changing climate. Most of all, in the United States, but even somewhat in the UK, Canada, and Australia. Why is that? It’s because people throw up religiousy-sounding objections to explain why they reject the science. Rejections like, “If God’s in control, humans could never affect something as big as this planet” or “In the Bible it says there will always be seasons” – never mind the seasons are caused by the orbit of the Earth around the sun and they can’t be affected by global warming – or “The world’s going to end anyways, so why does it matter?” But when you actually go to what the Bible says, it doesn’t say that.

In the first book of the Bible, Genesis, it says God gave humans responsibility or stewardship or dominion over the Earth. That means he gave us the ability to care for. or exploit, the Earth, number one. And then, at the very end of the Bible in the book of Revelation it says God will destroy those who destroy the Earth – so clearly others besides God have the ability to destroy the Earth – and no one questions the reality of nuclear bombs, right? And all the way throughout the Bible it takes about God’s love and care for creation, about the idea of stewardship and appreciation of the resources we have, and even more so about loving and caring for other people who are being affected today by a changing climate.

I care about climate change because it affects things like poverty and hunger and diseases that nobody should be dying from in 2017. We care about it because it isn’t only an environmental issue that environmentalists care about. It is a human issue that every human would care about. Even though faith looks like a barrier today because of all of the religiousy-sounding objections people throw out, the reality is that many people have confused their faith with their politics. Their statement of belief is written first by their political party and only a distant second by the Bible, and when the two come into conflict, politics wins out.

I think if people recognised what it is that they really believe, who they really are, that that is the motivation that many people need not just to change their mind, but – even more importantly – to care. That is the real barrier, not whether we agree this is real or not, but whether we understand that this is a critically important issue not just for the future of our planet in sort of a vague way, but the future of me, my family, my community and people who are poor and suffering all around the world.

CB: This leads me into my next question. From a UK perspective, we have a view of a big voting bloc in the US that’s conservative evangelical with a pretty sceptical view of climate change and that it’s caused by human activity. From your perspective, how realistic is that view?

KH: [Laughs] I am here today at the invitation of an evangelical organisation, A Rocha. When I was at COP21 in Paris, I was there with the head of the World Evangelical Alliance, who is an official delegate for his country of the Philippines and many other evangelical organisations from around the world. The National Association of Evangelicals in the United States and the Evangelical Environmental Network were two of the organisations recently invited to the Vatican to discuss world health and the impacts of climate change on our health.

The reality is that if we actually look at what we believe, it makes all the sense in the world – Christians should be the first person in line demanding action climate change. What’s happened in the United States is people’s faith has become so politicised now that I actually think it’s easier to think of people as two very distinct groups, with a little bit of overlap, but not that much. There’s the political evangelicals, the CNN evangelicals, the voting evangelicals, the ones whose statement of belief is written by their political party, not by the Bible. Could you really call them evangelicals? I don’t think so. Evangelicals are supposed to be spreaders of good news. Protestants are supposed to be people who rely not on multiple sources of authority, but on the Bible. Whereas, today, political evangelicals are relying on two sources of authority: their politics and the Bible, and when push comes to shove  they’ll go with the politics. That’s not even Protestant.

There is another group that is not as loud, but they are there. They are the evangelicals who believe what the Bible says. Who, when their politics and the Bible come into conflict, they’ll go with what the Bible says. They care passionately and deeply about this. One of my greatest pleasures is travelling around the country meeting all of these people who share the same heart, who share the same concerns, and who are involved in reaching people and talking about climate action because of who they are, not despite it.

CB: On a similar note, what messages or arguments do you find the most effective at communicating climate change to a conservative evangelical audience?

KH: So often we feel when we’re talking to people about a changing climate who either might not be totally on board with the science or – even more commonly – aren’t really on board with the idea that this is important, we feel that we have to instil new values into people – they don’t have the “right values”, so we have to make them care about different things than they actually care about. The reality is I am becoming increasingly convinced that just about every single person on this planet already has the values they need to care about a changing climate. They just haven’t connected the dots.

The key, when we’re talking to anybody, is to say, “What makes you tick?” Let me get to know you. Let me listen to you. Let me ask you questions. Let me figure out what I share with you. Do we both have a passion for birding? Are we both members of the Rotary Club? Are we both Christians or Muslims or Hindus or do we both belong to a specific faith tradition? And based on that, let me share with you from my heart why I care about a changing climate. Let me connect the dots for you between the values that we share – what’s already in our hearts – and why it makes all the sense in the world to care about this issue of climate change.”

I view what I do more as holding up a mirror and inviting people to look in the mirror with me and remind both of us who we really are and, in turn, to act like who we really are. That’s a much easier thing to do than to try to instil new values into anybody past the age of about – what – 10? [Laughs] So that’s an approach I think that we need to take with everyone, anyone from any part of the spectrum.

With Christians, the values we share are the idea that we have responsibility for this planet and that we are supposed to love and care for other people as we ourselves have been loved by God. Reminding ourselves of those common shared values, which are core to just about any part of Christianity – even though we may be divided on things like the colour of the paint in the sanctuary or what size cups of joy we get when we get to heaven – we are entirely united on those two issues. In fact, almost every major world religion or faith has those two core values in their faith. So we start with those values that we already share, and then connect the dots to a changing climate. And you don’t require a lot of dots to make that connection.

CB: Thinking about climate science communication more broadly, what do you think scientists tend to get right and wrong when communicating with the public?

KH: The very skills that make us good scientists are skills that often make us terrible at communicating. People often try to say there’s this whole spectrum of engagement and they try to figure out where on the spectrum should scientists be. I don’t think there’s any place where people should be. I think it’s a very personal choice where we fall on the spectrum. We need people doing really good research and publishing that really good research, increasing our understanding of our home, this planet. And, frankly, there’s some scientists who should never talk to the public [laughs], because that is not their forte. That is not what makes them excellent at what they do.

And then, there’s those of us who engage with other experts outside of our spheres – I work with civil engineers, water managers, city planners. Then, increasingly I go out and I talk to people and many of my colleagues are starting to do that, as well. Maybe they might talk to their child’s school or to a local community group or a special interest group. And then, we have scientists all the way at the other end of the spectrum – people who are chaining themselves to fences demanding action, motivated again by the shared concern for this planet that our research has shown us. So there’s an entire spectrum of engagement, and I don’t think anybody should tell anybody else where they should be on that spectrum. It is a very personal choice, because as academics we are not typically rewarded for any of this work.

We are rewarded for the research we do, the papers we write, the grants we bring in, as long as our teaching’s OK. But all of this extra outreach and communication engagement, many of us believe it’s part of our responsibility as public academics. But it’s not something that we are either trained to do or that we are rewarded for in our jobs. Because of that, I think it’s a very personal choice, because – depending on who you are, where you work, what you do, what things you’re good at, what’s your personality like and where you are in your career – you may feel more comfortable at a different place in that spectrum at a different time in your life. But wherever you are on that spectrum today, you’re doing something important.

CB: Do you think that scientists should be more formally recognised for the communication work they do? And if so, what form could that take?

KH: That’s a good question. I’ve been having that discussion with some colleagues. The system in which we work, we are trying to do 21st century science in a 20th century framework. We are often not rewarded for interdisciplinary work, which is exactly what we need to understand climate, let alone rewarded for outreach and engagement. So there has to be a fundamental change in our institutions, in the way we view academia and knowledge and science. That conversation, I think, goes beyond climate change. It goes to the issue of the world is changing; we are understanding how interconnected all of our systems are. You cannot sit over there and only study atmospheric dynamics because the atmospheric dynamics are intimately connected to the ocean, increasingly we’re understanding to the biosphere, which in turn is affected by human activities and human decisions. So all of a sudden you need sociologists talking to atmospheric chemists. You need people who study narrative and rhetoric to understand how we as humans tell ourselves stories, talking to someone who’s studying geoengineering. We need these communications and often our institutions are not designed to support and to recognise them. And unfortunately I don’t have a solution to that – I’m not a [university] chancellor! [laughs].

CB: You’re very active on social media – Twitter, Facebook, YouTube videos, etc. Why do you use it and what benefits do you see from it?

KH: I engage in social media because it’s something that fits into my life and reaches people, I think, that are interested in getting information. Some people blog; others do Twitter; some people do videos; others get out and talk to people. I think it’s important to pick things to do that you really enjoy. And so, when I travel, I enjoy Twitter because it just gives you these short bites and you can interact with so many scientists on Twitter. I think there’s more scientists on Twitter than any other social media platform in the world.

On Facebook, Facebook is unique because Facebook is where we interact the most with people who aren’t in our bubble. Why? Because we’re friends with our family and almost everybody has some family member or members – or sometimes their whole family – that are very different from them. So on Facebook, my goal is to share information and stories with people that they would feel comfortable sharing with their friends and family and colleagues even if they’re very different than them politically – or socially or culturally. Whereas, on Twitter, my goal more is to engage with the latest discussion on many of the new results that have come out, talk about the latest issues, and share ideas with like-minded people.

CB: What about pitfalls of social media?

KH: Oh, there’s many pitfalls to social media, and one of the biggest pitfalls is time. Time is the most valuable thing that we have. You cannot buy time. You can waste it. You can never get it back. And so, in doing social media, I know that several of my colleagues, Peter Kalmus [a climate scientist at NASA’s Jet Propulsion Lab] is one of them who wrote an awesome book on things that he and his own family did to lower their carbon footprint – I highly recommend Peter Kalmus’ book. And so, we were just having a discussion recently on how if you let yourself just keep scrolling through your Twitter feed, you could be there all day. You have to set very hard limits on how and when you do it.

For example, for me, with Facebook, I write a lot of my posts ahead of time and then line up a week or two of posts well ahead of time. And through sad experience, I’ve had to put a pretty strong filter on people’s comments, so I have a very long list of words that if people use any of those words, their comment will not appear on the page.

With Twitter, I mostly do it when I’m somewhere else and I have to just wait for a minute or two. Standing in line at the grocery store; picking up my child from school; standing on the jet bridge waiting to board the plane. Those are the perfect times to do Twitter. But to really do the research, you still need those uninterrupted blocks of concentration and you can’t allow social media to interfere with those because it will take over your life.

CB: Finally, I just wanted to ask you a couple of questions on the IPCC.

KH: Oh, yes.

CB: Firstly, what are your thoughts on the IPCC’s big assessment reports? Is this model the best way for it to be effective, or is there a better option?

KH: This is not going to be a popular answer [laughs]. The purpose of the IPCC assessment process is to provide a synthesis of the science that has been agreed upon ahead of time to use as the basis of the negotiations at the conference of parties [COP] to the UNFCCC. That is the purpose of the IPCC. So that is why there is this comprehensive assessment, and then the summary for policymakers has to be signed off by every country. And then, once you get to the COP you can’t negotiate the science anymore. You cannot argue over whether it’s warming, how fast it’s warming, how much is humans. Those numbers are in the IPCC and that is the basis which every country has to move forward.

Over time the IPCC has evolved into more than that. It doesn’t only provide information to the COP process, it provides information to the entire world. Everyone is waiting to see what the updates are on the climate science because we get hundreds of papers coming out every month. Nobody can keep you with the fire hose that is climate science these days. Many people rely on the IPCC as the most recent assessment of the science that they can use to make decisions, to understand their vulnerability, to look at mitigation potential.

But the IPCC is designed for the era when our resources were printed books. It’s designed for the era when you published a volume on paper with ink and when you wanted to reference it, you put it down on your desk and you opened it to page 982. We live in a very different era today. The first IPCC report was published in 1990, and today almost nobody uses printed books. I haven’t bought a printed copy of IPCC I think since 1995. I don’t know about you, but I use a Nook [e-reader] to do most of my reading. Unfortunately, the IPCC has not kept up with that. It is still being published as if it were 1990. And what’s the cost to that? The cost to that is you’re starting from scratch every time. Talk about inefficient. Do you know how many scientists, how many meetings, how much CO2 is burned going to those meetings it takes to write an IPCC report? The numbers are boggling and the vast majority of people are donating their time for free because they understand the importance of the assessment process.

I want to be very clear. I am not at all criticising the importance of this process – it is vitally important – and because it is so important, I think it should be done in the smartest and most strategic way possible. The smartest, most strategic way today, in 2017, is very different than it was in 1990. It’s to have a continuing, or sustained, assessment process where instead of starting from a blank page every single time, instead you have a living document that is updated on a regularly scheduled timeframe.

Now, you can’t update the document every time a new paper is published. You don’t want to do that either. The document should represent the balance of the evidence. And so, when one aspect of our understanding starts to change – looking at methane emissions from natural gas, for example – you don’t want to update the IPCC as soon as the first paper comes out. You can have a committee that meet every year, and they can say, “All right, what should we work on this year? What topics have a critical mass of evidence that has been amassed in the last few years to the point where we could really significantly update this section?” And so, every year they could schedule one or more sections for an update based on their expert opinion of the state of the science, but other areas where the science hasn’t really advanced much, you wouldn’t have to update them for three, five, possibly even 10 years. You might just have to update the figure. Global temperature change. You don’t have to change what the figure looks like, you just add a new data point to it.

I don’t think sustained assessment would actually be that hard, but the problem is that as a community we’re very conservative. Most people don’t recognise that, but we are very conservative. What do conservative people hate most? They hate change. It is really difficult to talk about changing the IPCC process without people taking it very personally because people have invested their lives in this process and many – again, as I have said – many have done it free of cost, sometimes even at the expense of their own careers. So in no way do I want to minimise the level of effort that has been put into this, but I think that since time is our most valuable resource, we should all of us be managing our time as wisely as we can. And producing a giant volume, which is numbering now in the thousands of pages, every five to 10 years from scratch is no longer the best use of our time in the internet era.

CB: So the IPCC is going to be producing several special reports, the first of which is on 1.5C and due next year. I wondered what your expectations are from that report?

KH: I think the report is an excellent idea because it is addressing a very important and relevant question, and that report is unusual. It’s not the typical working group one, two, three framework. That report is actually a synthesis of multiple groups, not just looking at what it would take in terms of the science to reach the target, but what are the impacts and even what are the ethical considerations of the target. I think this is a fantastic model where they’re finally start to merge the groups together to answer key questions that people really have.

CB: And in terms of what it might say?

KH: It’s too early to say that [laughs]. I haven’t reviewed the draft yet!

CB: And I just wanted to finish with one last question. Looking at the next generation of climate scientists coming through, considering that climate science is quite a partisan and potentially hostile career to work in, what advice would you give to that next generation?

KH: [Laughs] The next generation of climate scientists is very different than generations who have gone before. They tend to be much more socially aware. They’re studying this because they understand how important it is. They’re typically already engaged in outreach as a student, let alone as an early career faculty member. But they confront the same issues that those of us who do outreach do confront, which is, number one, the system in which we work is not designed to support this type of effort. I had someone say to me not that long ago that in a senior faculty member, a blog is a charming eccentricity. In a junior faculty member, it demonstrates a dangerous lack of focus.

The second hurdle that early career scientists face is the hurdle that we are not equipped in any way, shape, or form for all of the shots that are going to be fired at us as soon as we put our head up above the parapet. We are not prepared, often, for what’s going to happen. It can be so discouraging, not just the vicious hate, but the complete arrogance and disrespect. The idea that my opinion is more valid than your fact when we have been raised and reared in a system that values objective facts so highly. We almost deify them. We live in a different world and people are willing to engage today in a way that they weren’t before, but we need to stand together in a way that we haven’t necessarily done.

As scientists, we are often trained to look for flaws and faults in other people’s research, which will still do and we derive enormous enjoyment from doing that [laughs]. But, at the same time, we have to recognise that one of the most important things that we can do is support each other in this effort.

CB: Thank you very much.