This is part of an extensive interview conducted days after Veerabhadran Ramanathan, 81, won the Crafoord Prize (in Geosciences), often considered a precursor to the Nobel.
It was Ramanathan who discovered, in the 1970s, that chlorofluorocarbons (CFCs), common refrigerants at that time, were in fact potent greenhouse gases.
For half a century, his work has shaped our understanding of how climate works. His research has formed the basis of international agreements. He has advised four popes on climate change. Here’s more from the interview.
* In 1980, you published a seminal paper on warming…
Science has three parts. The first is asking what’s happening out there. We observe that CFCs and CO2 are rising, and temperatures are going up. That’s detection.
The second is attribution—what’s driving what. For that, you need both observations and models. With NASA engineers, I designed a satellite experiment to measure the different parts of the energy system to understand how the atmospheric blanket of gases traps heat. Think of it this way: sunlight hits the planet. About 30% is reflected to space; the remaining 70% heats the surface, the ocean, and the atmosphere. That heat is then radiated out. What comes in has to balance what goes out. We call that energy balance.
The CO2 envelops the whole planet like a blanket. It doesn’t create heat; it traps the heat (infrared radiation) trying to escape. So, the planet, like our body, has to get warmer to shed energy. People thought there was only one blanket. My CFC discovery catalysed the discovery of a whole set of blankets for different gases, like CFCs, hydrofluorocarbons or HFCs, methane, nitrous oxide, ozone. In 1985, I led an international team and showed that the non-CO2 gases were contributing significantly to the warming, depending on the timeframe. Suddenly, the problem was far more serious than was previously thought.
And that’s attribution, once you’ve done the detection.
* But if there were so many blankets, how was the observed temperature lower than the predicted temperature? Was there was something thinning out the blankets?
The final piece of science is prediction. If the blanket is thickening, the planet must warm. Working with meteorologist Roland Madden, we predicted — using observations — that by 2000, warming would rise above natural variability. It did. In 2001, the UN acknowledged human-caused warming. But the warming we saw was much less than what was predicted.
* How did you work to figure this out?
I don’t trust models unless observations back them up. Unless I can prove them myself, with data.
So, NASA engineers and I designed the Earth Radiation Balance Experiment (ERBE) with state-of-the-art instruments for measuring the incoming solar energy, the reflected solar energy and emitted infrared energy.
The data showed that the “blankets” were more complex than we envisaged.
Naturally occurring water vapor was the thickest blanket, the dominant heat-trapping gas. Models predicted that air will be more humid (that is, hold more water vapour) with warming, the blanket thickness will increase and amplify the warming. With great difficulty, I was able to persuade NASA to let me figure out an algorithm to directly determine this amplification of the CO2 warming by water vapor.
Theory predicted about a 7% increase in water vapour per degree of warming. When I measured the blanket in the tropics and over the polar region, I saw it was thinner in the latter, and very close to what thermodynamics would predict. Our data showed a 6.6% increase in humidity per degree of warming. Without this water-vapour amplification, climate change would be far weaker, and you would not be talking to me now.
That left the question of why the observed warming of the planet was not as large as predicted by models. Something else was cooling the planet.
Air pollution chemists were proposing that particles (also known as aerosols) from vehicles were cooling the planet by reflecting sunlight. But at that time, that was speculation. They had no direct data on how aerosols were changing the energy balance.
* Was this particle conversation an attempt to divert attention away from carbon dioxide?
In the 1970s and 80s, there was no politics, just scientists struggling with limited data. Nobody trusted the meagre data available could inform us of a global problem. You’d see a little bit of pollution from a fire, how can that spread around the globe?
Paul Crutzen — later a Nobel laureate — and I collaborated to solve this riddle. Paul, a close friend of mine, perhaps my best friend in the scientific field, focused on the chemistry.
My question was different: Do aerosols really travel that far, and do they cool the planet or heat it?
So, in the 1990s, we launched one of the largest field experiments, with over 250 scientists from the US, India, Germany, Netherlands, Francis and even Russia. We had instruments on four aircraft, two ships, hundreds of balloons and surface observatories. I had the honour of being the chief scientist. With instruments on the ground, in the air and in space, we launched the experiment over the Arabian Sea and the Indian Ocean, to measure aerosols and air pollution transported from South Asia. It quickly became, and still is, one of the most sophisticated aerosol experiments ever done.
Why the Indian Ocean? South Asia offers a natural experiment. In summer, winds bring moist air from ocean to land, making it rain. In winter, cold air sinks over the Indo-Gangetic Plain and flows out over the ocean, carrying everything with it. When I examined satellite data with my research team, we saw a massive pollution cloud, but we didn’t know whether it was natural or human-made.
* What confirmed that it was primarily caused by pollution?
The Maldives Observatory data showed us.
From satellites, we could see the cloud thickness gradually becoming thinner, thinner, thinner when we moved away from South Asia into the ocean.
At the observatory in the Maldives, we could literally “smell” the clouds with instruments. Chemists measured sulphates, nitrates, black carbon soot and organics in the brown clouds over the ocean, and their relative composition was similar to that from South Asia. It was the pollution. The black carbon trapped sunlight, but as a whole the cloud of aerosols reflected sunlight, and so we determined that the global cooling effect of aerosol can be substantial.
* Climate is not a subject that people vote on. How can we change that?
I hope political leaders surround themselves with good advisers and accept a hard truth: it’s going to get worse. Leadership means protecting people and helping them adapt to climate change. That requires experts, especially on the monsoon and changing rainfall.
I have seen what happens when drought lasts more than two years. In Maharashtra, we saw men leave. Then predators arrive from cities, luring young girls away. We know how that ends. These communities need energy, opportunity, and a belief that a dignified life is possible. Village girls must be educated so they can find real work and not be forced into migration or trafficking. Some of the spiritual leaders I’ve worked with in India are opening schools to prevent this from happening.
This is where my focus lies: the poor. Otherwise, we will see massive disasters.
That concern led me to the Surya project. Cooking smoke has conclusively been shown to kill at least two million people, mostly women and children. When a woman cooks, she often holds a child, the child inhales the smoke. We provided cleaner stoves and installed instruments to measure black carbon. Using this data, we were able to give carbon credits to the women. But I was unhappy with the stove design. It was fuel-efficient but not user-friendly. Women had to lift hot pots mid-cooking to add fuel from the side or bottom. The engineers said, “Use gloves.” I told them, “Try cooking in 110-degree heat wearing gloves.”
* With a child in your arms.
Exactly. It must be designed locally, for local conditions, with women involved in the design. My daughter Tara, who was my collaborator in Surya, put it bluntly. She said, “Dad, you guys are designing stoves; you don’t know how to cook.” My role was to expose the problem. Now others have to carry it forward.
(For more from Veerabhadran Ramanathan, click here to read his take on pollution, agriculture and India)
