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Discussion on climate change and health

Interviewer: Antoine Rondelet, Founder @ Ganddee

Guest: Andy Haines, Professor of Environmental Change and Public Health @ LSHTM


The London School of Hygiene & Tropical Medicine (LSHTM) is a world-leading university for research and education in public and global health, with a mission to improve health and reduce inequalities through research, education, and translation of knowledge. Located in the heart of London, the School has a long and distinguished history of addressing some of the world’s most pressing health challenges, from infectious diseases to non-communicable diseases and environmental and social determinants of health. The School’s research and teaching programs cover a wide range of disciplines, including epidemiology, statistics, health economics, social science, and public health. (More info here).

Andy Haines is Professor of Environmental Change and Public Health at LSHTM with a joint appointment in the Dept of Public Health, Environments and Society and in the Dept of Population Health. Previously director of the LSHTM for a decade and having been a member of numerous major national and international committees, Andy now co-chairs the InterAcademy Partnership working group on climate change and health, the Royal Society/Academy of Medical Sciences group on health and climate change mitigation, and the Lancet Pathfinder Commission on health in the zero-carbon economy, among others. (Full bio here).


Antoine: Before talking about climate change, I am keen to look at the current situation, especially look at the health impact of our current ways of living. It seems that our unsustainable ways of consumption come with a range of health challenges (e.g. air pollution, microplastics, processed food etc.), yet, life expectancy has dramatically increased over the centuries. It seems that we have tremendously improved global health by developing society in a way that made our environment more toxic. Isn’t there a little bit of a paradox here? What are your thoughts on this?

Andy (LSHTM): Absolutely, this is a really important paradox. Human health has dramatically improved. If you look at the middle of the last century, life expectancies increased by over 20 years. While there are still very big inequalities, of course, we have seen major health improvements around the world with sharp declines in infant mortality and maternal mortality for instance. Absolute poverty has also declined, especially prior to Covid. However, these improvements have come with a cost, and this cost has been borne by the Earth and by the natural systems of the planet. Since those natural systems: the climate, fresh water availability, soil health, plants, biodiversity etc., ultimately sustain human health, so far, our development has eroded the foundations of the health of human civilization. This has been driven by the consumption patterns, largely the consumption patterns of the so-called developed/high-income countries, and now also, emerging economies as they develop in the classic sense of the word “development”. Of course, those people who have been let behind, the poorest people, who often contributed very little to the climate crisis, are going to, are beginning to, and will increasingly experience the worst impacts of climate change. While no parts of the world will be immune from the negative effects of climate change, they are the ones who will suffer the most. So, we have this big paradox, which also leads to the debate around climate justice and the fact that emission responsibilities are largely from those countries which have already benefitted from the burning of fossil fuels and unsustainable approaches to development.

Could you explain what are the connections between a changing climate and human health? How can the former impact the latter, generally?

I think there are three broad pathways by which climate change can impact on health. If we look at the direct effects of increasing temperatures, for example, we know that death rates go up when populations are exposed to extreme heat. Indeed, there is an optimum temperature, which differs in different parts of the world, below which death rates go up, and above which death rates go up as well as people get more exposed to extreme heat. When it comes to heat exposure, there’s the potential for very major increases in death rates, particularly amongst the elderly, but not only amongst the elderly. It may be possible to adapt up to a point, but they are likely to be limits to adaptation, which we can talk about in just a minute. As we just said, heat does not just impact the elderly. Extreme heat also affects young people and pregnant women, for instance. We’ve been working on a paper, that got published a few days ago in “The Lancet, Planetary Health”, actually, in which we have documented the effect of extreme heat on pregnant women subsistence farmers in West Africa. In this study, we observe that extreme heat is having an effect on the fetus and that at the end of the shifts, both the fetal heart rate and the mother core temperature, have gone up, showing some of the effects of extreme heat stress. Those people are already operating very close to the kind of temperature threshold the human body can tolerate. We also know that there is a decrease in labor productivity in many parts of the world because of the increasing temperatures that people are being exposed to. On top of that, there are extreme events, like floods and droughts, which have, of course, physical health effects but also mental health effects. Droughts can affect crops, crop yields, nutrition, infectious disease transmission, population displacements, mental health impacts etc. We are also seeing the effects of climate change on wildfires, increasing wildfire exposure in some populations, and we now know that a few days following the exposure to wildfire smoke there is an increase in death from heart disease and from some respiratory conditions as well.

Then, there are the effects on food production. We know that climate change reduces crop yields, particularly in tropical and subtropical regions. It reduces the yields of staple crops like the cereals that people eat, fruits and vegetables, and it can affect livestock productivity as well. That threatens food security in many parts of the world, and although there may be increases in productivity in the temperate areas, we don’t know how long it will last for, nor do we know whether populations will be able to afford to buy food on an increasingly competitive international market. We also know, on the food level, that climate change does not only impact crop yield. This is not just about the amount of crops, but it’s also about the nutritional state of the crop. As you put more carbon dioxide into the atmosphere, you can stimulate the growth of some crops, but they contain less micronutrients. Given that already probably about two billion people are suffering from micronutrient deficiencies, any decrease in micronutrients is obviously a great concern.

And then, moving forward, of course, infectious diseases. Climate change can affect the incidence of all ranges of diseases: waterborne diseases, foodborne diseases, but also vector-borne diseases like dengue, malaria, and a whole range of infectious diseases. One estimate recently suggested that about 58% of infectious diseases could be affected by climate change, at least in theory. There could also be some very worrying surprises ahead. In the thawing permafrost in the Arctic and sub-Arctic regions, there are organisms trapped within the ice that have become adapted to cold and which could be released as the ice melts. We don’t know what the implications for human health this would have, but we do know that there are bacteria that are known to be pathogenic to humans. There are also toxins, mercury, radioactive waste, there are a lot of different things buried in the ice that could be released as the ice melts.

Finally, there are the effects of climate change on social determinants of health. What I mean by that is, increasing poverty because people can’t work as much or because their crops are failing, displacement of populations because of floods and droughts, and then possibly, even increased risks of conflicts or conflicts. So, there are a lot of reasons to be concerned and many different pathways by which climate change can impact on human health. And of course, climate change is just one of a number of environmental changes occurring including biodiversity lost, land use change, depletion of fresh water, and so on. So yes, it’s clear that climate change and other environmental changes can profoundly impact on human health in different ways depending on where you are in the world.

The consequences of climate change on human health are numerous. We seem to be attacked from all fronts, and we have limited resources to face these threats. Is it possible to identify, out of this long list of consequences of climate change on human health, the biggest potential threat to health? If so, which one is it, to the best of our current knowledge, and why?

Well, I think obviously heat itself is really important, particularly in those parts of the world where populations are already exposed to extreme heat. We saw these terrifying heatwaves for example, in India and Pakistan earlier this year, when people were exposed to such high levels of heat, it was very close to the levels of physiological tolerance which we can adapt to. And of course, many of these populations don’t have access to air conditioning and even if they do, often, the grid fails in the context of these heatwaves because so many people turn on their air conditioning. Of course, air conditioning itself creates additional problems: you need to burn more fossil fuels, need more energy, you increase the urban heat island because you pump the heat outside the buildings and so on. So, heat is certainly one area. I do think these very large disasters, like floods and droughts, as we’ve seen in Pakistan, are really important for human health. Infectious diseases are also very important. Some are easier to adapt to than others, but the problem is that, it’s not just one single threat we’re having, it’s a multitude of challenges at the same time, which makes it much more difficult to adapt to. So, you know, they’re all important. That’s the problem. They are all causing concerns and, you know, in a way it is the additive effect of these multiple changes that is particularly worrying. If we only had one challenge to face we could isolate it and think about how to address it, but the problem is, we’re having to address multiple challenges at the same time and that’s causing considerable concern for the future.

We’ve talked about all the various threats we’re facing now, which is quite concerning. This is not good news, obviously, and we need to do something about it. What are the health benefits of climate action? How can climate mitigation improve human health?

There are two types of action that we can take. One is to adapt to the climate change that we can’t prevent. We have to adapt better because we are already at about 1.2 degrees, global average, temperature increase, and we have to deal with the effects of this temperature increase as best we can. There are different approaches to adaptations whether initiatives like disease early warning systems to get early warning of, say, an outbreak of vector borne disease or, heat early warnings systems or natural disaster early warning systems, to prepare against floods, droughts etc. There’s also a lot of work going on in thinking about how to make healthcare systems more climate resilient, such as, ensuring that supply chains can withstand extreme events, that there are cool spaces where vulnerable people can be kept cool, but also identifying vulnerable populations in the community. That being said, the funding in adaptation measures is currently insufficient, and evidence is not always complete. We don’t fully know what are the most cost-effective ways of adapting in different situations, particularly in low and middle-income countries.

The other type of action we have to take is mitigation, i.e. cutting greenhouse gas emissions, rapidly. If we have any chance of reaching the Paris Agreement, we need to cut emissions by more than seven percent year-on-year, just to reach 1.5 degrees, which, of course, is not happening, and we have less than 10 years of emissions at current levels left to meet the target, or have a reasonable probability of meeting it. Even if we take the two-degree limit, we only have about 25 years of emissions left at current emissions levels, or something of that order. So, we have to act very quickly, and we’re not. We’re not, as we know, acting at the necessary speed and scale.

The important message here is that, there are near term benefits to health through rapidly decarbonizing the economy. Over and above reducing the risks of dangerous climate change, there are other benefits to health in undertaking mitigation actions. For example, as we phase out fossil fuels, we also create much less air pollution, and we know that air pollution, much of it from fine particles that go deep into our lungs is a major killer according to various estimates. One estimate, I was involved with, suggests that 3.6 million deaths are caused every year from air pollution from fossil fuel burning alone, and there are other causes as well. These are potentially preventable deaths. If we can phase out fossil fuels, we get these double duty benefits. Actions to mitigate climate change can not only benefit the climate, but also benefit health in the near term.

On another note, we know that the food system is a major driver of biodiversity loss but also contributes to climate change perhaps almost a quarter of the total greenhouse gas emissions, if you put food systems and land use together. This is because our current food system is based on unsustainable approaches to growing food, a dependence on grain-fed meat, for example, particularly from ruminants, and we know that ruminants produce a lot of methane etc. As such, reducing red meat and dairy in high consuming populations while consuming fruits, vegetables, nuts and seeds, for a healthier, more plant-based diet, can make a contribution to both improving health, potentially preventing millions of premature deaths a year, but also reducing greenhouse gas emissions.

Another example of how climate actions can improve health could be given by looking at transport systems. At the moment, transport systems are a major source of air pollution but also greenhouse gas emissions, partly because of the dependence on the private car. Moving towards more sustainable transport systems with not just cleaner engines, such as electric vehicles, can obviously reduce air pollution, but they don’t necessarily bring all the other benefits of increased physical activity you get with walking, cycling or using public transport. So, there are all sorts of benefits that could occur as a result of more sustainable transport policies.

These are just three examples. I could give others as well, but these are three big ones.

You mentioned that funding was insufficient for adaptation measures etc. That’s interesting because earlier in this discussion you also mentioned the impact of climate change on productivity. From an economic standpoint, I don’t understand how funding could still be insufficient, while scientists and economists have proven over and over again, that uncontrolled climate change would actually be a disaster for the economy. It just seems like the obvious thing to do. The amounts that need to be invested to adapt to climate change and mitigate it are small compared to the economic losses that would otherwise occur if nothing was done. I mean, from a purely economic standpoint, the lack of investments makes no sense at all…

Well, it is counterintuitive, but there are good reasons, or rather there are bad reasons for it. I mean, one, of course, is the fact that the fossil fuel lobbies are extremely powerful. They have unfortunately caused a lot of harm by circulating a lot of disinformation about climate change, the costs of mitigation etc. However, there are technical problems as well. There is the issue of intermittency for energy sources. With nuclear or fossil fuel power plants, you could just keep on generating electricity regardless of the weather conditions, whereas solar panels or wind farms have respective issues when the sun doesn’t shine, or when the wind doesn’t blow. More investment is needed in sustainable technologies and to improve energy efficiency. For instance, we should be insulating our houses much more effectively, so we don’t waste most of the energy we produce. Had we done that already, we wouldn’t have had the current energy crisis, or at least it wouldn’t be as big as it currently is. So, much more investment in clean technologies are needed, but powerful interests are in the way. We should also note that politicians have very short-term goals and aren’t thinking about the medium to long-term welfare of society, unfortunately. Their main concern has to do with staying in power for the next election. That generally requires very short-term policies, which may not be in our interests in the long term. This is a fundamental challenge, and even when policies are enacted, execution lacks. We still haven’t seen the hundred billion dollars a year promised at the Paris Agreement, which is not actually a lot of money in international terms. This in itself is a big worry, and I think low-income countries are quite correctly criticizing high-income countries for their lack of action and their lack of commitment. At COP 27, we also saw the agreement to set up a new loss and damage fund. Now the question is, how much money will go into it? Who will make decisions? How will they make the decisions and what will it be spent on? There are still a lot of question marks, even if the principal has been accepted at COP 27.

Yes, and we’ll see if countries deliver on the promises they’ve just made at COP15 in Montreal…

Yes exactly, that’s another one, and the US wasn’t even there in Montreal.

And President Macron was cheering for the French football team at the World Cup in Qatar, so well… Another quick thing I wanted to bounce upon was the fact that you highlighted that we had to act and do so very quickly. Time is running, and we only have around 10 or 25 years left, depending on which threshold we’re targeting. This channels back to an interview I made with Keywan Riahi during which we quickly alluded to the bootstrapping costs of the green economy. We know how to manufacture and install solar panels, set up wind farms etc. burning fossil fuels, but we’re still very reliant on fossil fuels to bootstrap these new industries. Concrete, steel etc. are still needed and are high emission sectors, so, connecting back to what you mentioned with air pollution etc., it feels like we need to burn even more fossil fuels now and do so very quickly to accelerate the transition to a more sustainable society, which may exacerbate the very issues highlighted before such as air pollution issues, etc.

This raises the issue, also raised but the IPCC, around demand reduction. At the moment, most of the future scenarios are all about “how do we just generate more clean energy?”. But it is worth asking: do we need to use all that energy? Do we need an economy purely based on more and more extraction of primary resources and where people consume more and more goods which they don’t necessarily, in a sense, need in order to improve the quality of their life? These questions lead to concepts such as the circular economy, the shared economy etc. We’d need to rethink our recycling processes, reuse more, share more resources etc. But such transition is quite radical. The combination of demand reductions and the circular economy is a pretty radical way of rethinking society, and I don’t see any Western politicians capable of having that discussion and raising those kinds of issues to the public. I’m not aware of any major political forces around the world that are saying these kinds of things to the public and say: “we’re going to have to change the way in which we live”.

I think politicians are still frightened to doing that. It’s a mistake to think the politicians lead. They don’t lead opinion. They don’t lead, they don’t develop new ideas. They are essentially followers, they will follow where they think the votes are most. I’m not saying all, but most of them.

Yes, and so do companies in a sense. If a company’s products are heavily consumed, and if a company manages to achieve its capital accumulation objectives, it doesn’t make economic sense for a company to change its business and strategy. They will align with what their customers want.

It is actually, yes.

Before we wrap up, I would like to quickly touch on Covid. What has Covid-19 taught us in terms of health risk management and in terms of our capability to face pandemics?

Covid provided a very mixed picture.

On the one hand we faced real problems in containing the spread of the pandemic in the early days, mistakes were made in terms of population movements, travel and so on. There was also a lot of disinformation about Covid, about the vaccines, treatments and so on. This massive misinformation and disinformation around the world, caused a lot of distrust of authority. There were also profound issues of inequity. Developing countries struggled to get access to the vaccines etc. Fortunately, sub-Saharan Africa wasn’t as impacted as many people feared for a variety of reasons, partly because it has a young population etc. The exact reasons are not entirely clear as far as I know, but fortunately, there weren’t as many deaths as one might have feared. Other parts of the world like Brazil, India, and China, which is now coming out of lockdowns, however, did suffer major increases in deaths. Overall, I think there were a lot of negative lessons. That being said, there were some positive lessons. Covid has reinforced the need for international cooperation, which wasn’t forthcoming. It reinforced the need for UN agencies like WHO to be adequately resourced, which they aren’t at the present time. It reinforced the need for effective research that could be conducted by in real time. It reinforced the need for more partnerships between the public and private sectors, and it also reinforced the importance of increasing the integrity of knowledge and in combating mis and disinformation. While difficult to do, I think some of the fact checking websites did a very good job. If people cared to look at them, they could have learned a lot from them. Another lesson taken from Covid is that the countries which looked very strong on paper didn’t always actually perform very well. Look at the US, if you looked at it on paper it was rated very highly in terms of its pandemic preparedness, but it performed poorly. Likewise for the UK. Despite the fact that it has got a universal access healthcare system, it didn’t do very well either, probably because mistakes were made fairly early on in the pandemic. Political factors over and above the technical capacity of public health and healthcare systems are really important, and I think Covid did emphasize the need for universal healthcare and the fact that we need to move forward on that agenda of ensuring that everyone is covered with access to effective healthcare. We are still seeing the big impacts of Covid on our healthcare system here in the UK, and I think many other countries are still struggling to cope with its aftermath.

And to your point, we are having this discussion in the middle of an ambulance and nurses strike here in the UK.

Exactly, yes.

Thank you so much for your time, Andy. Is there anything you’d like to mention or share with the community? (a book you’ve written? A paper that got published? Something, on climate, you’d like more people to be aware of?)

Well, I mean, if you’re asking me to do a little bit of self-advertisement, we did write a book on Planetary Health, published by Cambridge University Press last year, myself, and my colleague, Howard Frumkin. The book lays out many of the issues around how environmental change is undermining the prospects for human health and what we need to do about it. So, we have our book but of course many publications which you can find online and download.

There was also The Rockefeller Foundation–Lancet Commission on planetary health that I had the honor of chairing, published back in 2015 in the Lancet Medical Journal, and there are also many papers on the effects of climate change, written by an increasing number of people within the research community. The community is still quite small, but it is growing quickly, and the evidence base is improving quite quickly, so there is an increasing amount of literature out there.


Further reading:


We originally published this interview on OCRA, a climate forum and community that we started. This interview has been moved to our blog following the closure of the OCRA forum.

Ganddee interviews offer an opportunity to put some guest community members at the center stage. During these interviews we ask questions to our expert guest to better understand their work, learn from them, and understand how they contribute to the fight against climate change. We hope these interviews will serve as an invitation to expend the discussion on the forum.

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