Tracking Worldwide Air Quality: A Q&A With Berkeley Earth Climate Scientists

Air pollution is responsible for nearly four million deaths annually around the world, making it one of the defining global health challenges of our time.

Berkeley Earth’s early research on air quality estimated that China’s emissions from coal-based electricity alone was responsible for upwards of 400,000 annual deaths.

Following April’s National Geographic cover story featuring Berkley Earth’s open-source air quality data, we sat down with Berkeley Earth’s climate scientists Dr. Robert Rohde and Dr. Zeke Hausfather to discuss global air quality trends.

A full transcript of the interview is available below.

Kari Hulac (00:12):

Hello, I’m Kari Hulac, social media manager for Berkeley Earth, an independent non-profit organization focused on global temperature and air pollution data science. Joining me today to discuss the Berkeley Earth air pollution work is Lead Scientist, Dr. Robert Rohde, and Climate Scientists, Dr. Zeke Hausfather. Thank you for joining me today, Robert and Zeke.

Zeke Hausfather (00:36):

Thank you.

Kari Hulac (00:40):

Let’s start off by giving our listeners an overview of Berkeley Earth air quality data. Maybe share how the data is collected and turned into useful information for the public. What makes it different from other sources of air quality information? And Robert I’ll let you start with that.

Robert Rohde (00:57):

Okay. So for several years now, Berkeley earth has been collecting air quality data from a variety of governmental sources around the world. Typically these are monitoring stations run by national governments to keep track of their own conditions, but we then interpolate this data and, you know, across most spatially inside the countries, but also across boundaries to create real-time maps of fine particulate matter air pollution. So fine particulate matter, also called PM. 2.5, is the kind of air pollution that is the most hazardous to human health among air pollution you would commonly encounter anyway. So we’ve created these maps that give you a real-time sense of what’s going on because there are, that’s different from a lot of other sources of air pollution data, which is just very point oriented. And in addition, when you visit our website, we give you a lot of information about historical conditions. So you can look back if you’re in the US, you can look all the way back to 2004, for other countries it’s not so far, but you can get context across several years, so you can have an idea of what’s going on. And most other web portals and sources of air quality information, don’t look at the long-term perspective like that. So we’d like to give you a context of what’s going on.

Kari Hulac (02:30):

It would seem obvious to some people, but could you highlight some of the top reasons why this work is so important, especially at this point in the world’s history, in terms of climate change and other weather and you know, kind of some of the data?

Robert Rohde (02:46):

So one thing that a lot of people don’t realize is that air pollution is a contributing factor in more than 4 million deaths. You know, it contributes principally to disease. It contributes to diseases like lung cancer and constructive pulmonary disease, which is fairly obvious. You’ll get bad stuff in your lungs, you have trouble breathing. But it also contributes very strongly to heart disease and stroke. And what’s happening is that these fine particulates, which contain things like sulfate and heavy metals and nitrous oxides settle deep into your lungs and can move into your bloodstream. So you get a little bit poisoned by this air pollution that then contributes to the, all these negative health effects. So it’s –

Kari Hulac (03:38):

A million deaths

Robert Rohde (03:40):

More than 4 million deaths a year have air pollution as a contributing factor.

Zeke Hausfather (03:46):

There’s also some relation between air pollution and climate change. The burning of fossil fuels, which is the biggest contributor to the climate change we’re experiencing is also one of the bigger contributors to air pollution. Particularly in regions like Southeast Asia, coal-fired power plants are a big producer of sulfur dioxide and other sulfates. Vehicles, diesel trucks in particular are a big contributor to nitrogen oxide, emissions, and NOx, which is a precursor to PM 2.5. And so a lot of the actions that we as a society will have to take to reduce our greenhouse gas emissions will also have co-benefits in terms of air pollution. But there’s also natural contributors to air pollution that themselves may have climate links. For example, we see huge spikes in bad air quality associated with wildfire events in places like the Western us. And there’s a growing sort of scientific consensus that climate change has played a fairly large role in making these sort of extreme mega fires much more common than they were a few decades ago. And the associated air pollution events much more common

Kari Hulac (05:01):

That was actually my next question so that’s perfect. I wanted to learn more about the natural-slash-man-made factors that contribute to making air unsafe to breathe. So you touched on a couple of them.

Zeke Hausfather (05:13):

Yeah, I should mention that there’s also some natural factors that are not related to climate change. So for example, there’s some parts of the world that have very severe dust storms that can result in bad air quality and that, you know, have sort of always happened. And there’s not, at least to my knowledge, much evidence of human influences, making those worse outside of things like deforestation that can increase the amount of available dust to be in the air.

Kari Hulac (05:40):

Are there some locations kind of again, to get into this a bit, but that are just inherently have better or worse air or is it always a combination of man and nature?

Zeke Hausfather (05:51):

So there’s certainly small island nations tend to have good air, in part because whatever they emit can just blow over the ocean. So, you know, Hawaii, for example ishas pretty good air quality, usually because even if they’re burning, you know, diesel to generate electricity, they can – or even bunker fuel, which they do in a few cases, which isn’t allowed in the mainland – it mostly gets blown out to sea. So Robert can probably speak to this as well, but I think there certainly is a role of large landlocked areas, or, you know, though coastal China too, is some pretty severe air quality issues.

Robert Rohde (06:28):

Yeah, you’re absolutely right. Honolulu is one of the cleanest cities in the world. These Island nations, also some of the less populated Scandinavian countries. There’s a number of places where the air is quite a bit better, in part because it’s remote, they’re not getting as much air pollution from other sources. They’re getting a lot of good air off the oceans. And there are places where you have worse air quality for natural reasons. The Middle East and Central China are both places where you have substantial dust storms that just occur naturally with some regularity. So you’re always going to have a higher level of air pollution in some of those settings. However, the dust storms are still somewhat qualitatively different from the air pollution we get in China and India from the burning of fossil fuels, the burning of biomass and all of these things that are definitely human related and that the human activities is a large part of the health impacts that are affecting many places, such as Southeast Asia.

Kari Hulac (07:42):

And that’s kind of my next question as well. So the April edition of National Geographic magazine had an infographic and an article about air pollution that drew from Berkeley earth data highlighting the fact that the world’s 50most polluted cities are in Asia, particularly China, India, and Pakistan. So maybe talk a little bit more about that article or what trends you’ve seen in those hotspots.

Robert Rohde (08:08):

So Southeast Asia and also parts of the East are among the most polluted locations on earth. And a lot of that has to do with the burning of fossil fuels and the burning of biomass and other human activities. In recent years, we have seen a greater awareness of the harm and impacts that this is creating in places like China and India. Both of which are trending in the right direction, more slowly, and my hope particularly in the case of India, but you know, there is a certainly a concern and awareness of how serious this air pollution has become and a desire to improve things. Though it will take a substantial amount of time to deploy the technologies and to change the habits, to reduce the amount of emissions they’re creating.

Kari Hulac (09:13):

You both know Berkeley Earth did a study a few years ago that looked at the use of coal-based electricity in China, which at that time was linked to somewhere between 84,430 to 400,000 annual deaths. So now five years later, the use of coal is declining in the US and Europe, but not in Asia. So this is among your areas of expertise. Maybe you could start with how you’ve seen this energy source impactAsia’s air quality. You mentioned it a little bit earlier in our conversation today…what needs to be done about it?

Zeke Hausfather (09:49):

So coal is not the only contributor to PM 2.5, but certainly in Southeast Asia, it’s one of the major ones. And we’ve seen, you know, a huge build out of coal in China in the 2000’s and in early 2010’s. Since then coal use has largely peaked. And while they’re building more plants in recent years, the what we call capacity factor of those plants has been going down. So net today, the typical coal plant in China is actually run less than 50% of the time, in part because they overbuilt them a fair bit. So we’re not necessarily seeing an increased use of coal overall in China. But we’re also not seeing the types of decreases that we’ve been seeing in places like the US and Europe. Now there’s a lot of people who are very hopeful that some of the recent pronouncements by the Chinese government, and they’re, you know, very public commitment to get to net zero by 2060 might lead to some near-term pressure on the coal sector.

Zeke Hausfather (10:46):

But it’s too early to tell how that is going to pan out. And there’s been some fairly mixed signals so far. So, you know, we’re hoping at least in China to see a decline in coal use in the next few years. That said, there’s other parts of Southeast Asia, like Indonesia or Vietnam that are still building a fairly large number of new coal plants. And so while, you know, reducing coal use – and India for that matter is building new coal plants too. And so things are starting to move in the right direction for China. You know, it’s not necessarily clear that the same is going to be true for all of Southeast Asia.

Robert Rohde (11:21):

Something I would add, particularly in the context of coal, is that it’s not just how much you use, but it’s also how you are using it from an air quality perspective. With appropriate control technologies, a power plant can reduce their emissions by 90 or 95% in terms of the air pollution they’re putting out, while they’re still burning coal. Historically there have been issues with the deployment of these technologies and the compliance of getting them used. I think in the case of China, you’re seeing more robust usage of air pollution controls at the large scale than you used to. Although that’s not necessarily the case in all countries that are burning coal. And you also have issues with small-scale coal use: China historically has had a policy of giving people in cold parts of the country free coal to burn for their homes, which, if you burn into the home, there’s really no pollution controls, and you get a lot of pollution in the atmosphere. And they have only fairly recently started embarking on policies to reduce the amount of coal that is used on the small scale as well. And that will also have a marked impact on air pollution. We certainly hope.

Kari Hulac (12:53):

So. Moving on from China, you saw a trend last year where most of the world’s major cities had better air in 2020 compared to 2019, mainly as a result of the coronavirus shut downs. So share your thoughts on this was this surprising or not. And now that some areas are opening up, will this phenomenon have any lasting impact on public awareness or policy, or will we just be back to the same old, same old?

Robert Rohde (13:25):

So in 2020 we had lockdowns in various parts of the world at various times. The effect of those lockdowns tend to be on transportation and transportation fuels. There’s fewer cars on the road. There’s fewer jets in the sky. So there’s a lot less oil being burned. And as a result, you tend to see significant reductions in nitrous oxide pollution in many of these large cities where they had lockdowns. You might see a 15 or 20% reduction in the associated PM, 2.5 for a period of time. Most of those lockdowns were fairly temporary. But it is a noticeable thing for some of these cities where they have high levels of automobile pollution, whether that becomes a lasting commitment. It’s hard for me to know. There are examples of people celebrating the clear skies in parts of India, but whether that’s enough to really motivate people to clean up in the longterm or move more quickly than they are in cleaning up. I don’t know.

Zeke Hausfather (14:44):

There will probably be some long lasting effects, though I suspect it’s, it’ll be more clear cut in places like the US and Europe than say India and China. In the US we saw a very rapid acceleration in coal retirements during the coronavirus pandemic, in part because it was having trouble competing against other energy sources in a period of low demand. But alsoin the US at least we tend to see, or at least the last time we had a big recession, during the financial crisis, we saw a very pronounced long term effect on transportation behavior. People started driving a lot less after 2009, and in fact had only gotten back up to 2009 levels of per-person driving by 2019 when the coronavirus hit. And so given, the changes that have happened in our lives around remote work, around remote conferencing, while some of that’s going to come back, not all that will. And I suspect we’ll see some longer-term declines and transportation emissions that lasts beyond 2020.

Kari Hulac (15:48):

So the message here is all about what we decide to do with how we get to work and what kind of cars we drive.

Zeke Hausfather (15:57):

Yeah. I mean events like COVID-19 could really shake things up in a way that can accelerate transitions. And so, you know, we’re all sort of waiting to see exactly what’s the recovery globally will look like and what sort of technologies will be favored and what governments will do in terms of expenditures. But you know, we’re probably seeing things move a little faster than they otherwise would.

Kari Hulac (16:20):

So despite that bright spot with some parts of the world, the US then was hit hard last summer by – and some other parts of the world – by one of the worst wildfire seasons in history. And this year is shaping up to be extremely severe due to drought conditions. So what do we have ahead of us in the near future for air quality, as it relates to wildfire smoke?

Robert Rohde (16:48):

The wildfires are a major source of natural, air pollution, fine particulates in particular. And the US has in recent years had several major wildfire events contributing to air pollution, including last year’s wildfires, which temporarily caused the US averages for air pollution to be the highest they’d been in 15 years. So these events are really shaping, you know, making an impact on the trend for the US in terms of pushing us in the wrong direction towards more air pollution over time. And there are very pronounced impacts on local communities when you are near these things. You know, people in California for example, certainly very aware of how the smoke blows in… It smells terrible. You feel awful, you don’t really want to be hanging out and that’s conditions.

Robert Rohde (17:59):

And what we know is that climate change definitely has a role in making wildfires more common and more severe. And to the extent that that continues, we have to be prepared for more of these massive smoke events in places like the US, also some other places. And, you know, Australia had huge wildfires a little while back, some places in Europe as well. It’s just, you know, it’s one of these things that we have to be prepared for, because we’re not going to change turn the tide on climate change overnight. It’s going to take awhile.

Zeke Hausfather (18:41):

And it’s also important to point out that even if we were to wave a magic wand and cut all of our climate emissions to zero, our greenhouse gas emissions to zero, the Earth wouldn’t cool back down for many centuries to come. And so the conditions that are driving current wildfire activity are not necessarily going to get better at least from a climate standpoint. The best we can do is keep them from getting worse.

Robert Rohde (19:06):

And from my management perspective, I think we need to be prepared on the ground for figuring out how to fight these fires better, how to prepare the landscape so that there’s less material to burn. I think there’s a lot of things that we have to start considering in terms of a wildlands-management perspective to make these events less severe. And that will take time and money and planning. It’s not necessarily an easy thing to do.

Zeke Hausfather (19:41):

Yep. I agree with Robert on that. But for the near term, you know, we should be used to having a “smoke season” in the West, in addition to our rainy seasons and our dry seasons.

Kari Hulac (19:53):

Wow. That’s, that’s an interesting concept…as you and I live in California Zeke, we know, we know that smoke season! It’s definitely a reality. You mentioned funding Robert and I wanted to ask either of you, both of you…funding for air quality mitigation and, and research and such is only like 30 million globally. So a tiny amount. I mean, how important is for governments to devote money to fighting air pollution and, or, you know, like you said, for wildfire mitigation. Any thoughts about that?

Robert Rohde (20:36):

Yeah, I think there’s, there’s a lot of parts of the world where we really don’t even have, you know, established monitoring. And there’s a lot of places where a relatively small investment in money could provide a great deal, more information. I think that information and awareness is likely to drive public concern and drive the efforts towards mitigation, the efforts towards finding technologies that are less polluting. So I do think there is a potential for a relatively small amount of money to have an impact here in part, because there’s not very much money is spent on air quality in many parts of the world

Kari Hulac (21:24):

That makes sense. Zeke…you’re, you’re very well-versed in the policy side. Are there recent policy advances or new technologies that give you hope for mitigating air pollution and improving air quality?

Zeke Hausfather (21:43):

So I think that what gives me hope is the co-benefits between climate mitigation, which the world is really, you know, accelerating on and air quality improvements. And in fact, in many cases, the benefits of reducing fossil fuel use are larger from an air pollution standpoint than they are from a climate standpoint,. The longer term is a bit more complicated. And so, you know, I think that the rapid growth we’re seeing in the installation of wind and solar power, and in nuclear in places like China, the rapid adoption of electric vehicles worldwide, that’s really accelerating today. All of these things will play a pretty big role in reducing the sources of conventional air pollutants. And hopefully in a way that, you know, is win-win for everyone, right? These are new technologies that are in many cases cheaper than the alternatives they’re replacing.

Zeke Hausfather (22:39):

And so I think that will hopefully solve a lot of the air quality problem as well as solve the climate problem. And the two will hopefully go hand in hand. Now where there is a little bit of interesting complexity, is that a lot of the drivers of the most dangerous types of air pollution, like sulfur dioxide, also have a big effect on the climate, but not in the way you might expect. Sulfur Dioxide in particular has a strong cooling effect when it’s in the atmosphere. And so when we cut conventional air pollutants and aerosol emissions, we actually ended up with some near-term warming of the planet. Now that isn’t necessarily a bad thing on balance because the impacts of these air pollutions on health are so bad. And it is something that we already take into account in all of our various climate models. But it does make, you know, avoiding certain levels of climate change harder than it would otherwise be, if these air pollutants didn’t have a strong cooling effect on the planet.

Kari Hulac (23:41):

Interesting, definitely complex. I guess we’ll just close out by asking if our listeners want to take action about problems of air pollution or global warming what would you suggest individual people do and how can the public have more of an impact?

Zeke Hausfather (24:05):

I mean, from my standpoint, particularly when we’re talking about issues of air pollution the biggest thing that people in the general public can do is vote for politicians who are going to effectively address it. At the end of the day climate change and particularly air pollution is a policy problem. It’s a regulatory problem. It’s not like people voluntarily driving their cars less is going to make a huge dent in particulate matter concentrations versus regulation of new vehicles or requirements of catalytic converters. So that sort of thing. And so I really think we need smart policy around this. And I think we need to have governments invest in making alternative technologies cheap, so that it is easier for poor-to-middle income countries like India and China to adopt them in a wide scale,

Kari Hulac (24:58):

Anything to add in closing Robert?

Robert Rohde (25:02):

Yeah I would agree with Zeke there that I think in terms of solving the air quality problems, the biggest effect is going to be public policy. So it’s really about, public awareness and getting politicians – you know, talking to your politicians and getting the political establishment on board with things that are in many ways, beneficial already, such as increasing renewables, a decrease in coal, moving to electric vehicles, these sorts of things. We’ll reduce the air pollution, and if we make them cheaper and easier and more widespread, then we will be better off in multiple ways.

Kari Hulac (25:49):

Great, great. Well, thank you both so much for joining me today. I’d like to close by reminding our listeners that Berkeley Earth is an independent non-governmental source of vital climate change data. We hope you’ll donate today to support our research and for more real-time air pollution data, visit

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