Hansen and Ramanathan, Two Scientists Who Brought the World Face-to-Face with Global Warming—2018 Tang Prize in Sustainable Development
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(This article is the outcome of a project collaboration between the Tang Prize Foundation and Pan Sci Taiwan)

Chinese original by Chang-Chih Pan

If levels of greenhouse gases continue to go up, energy imbalance and an increasingly warmer climate could create a global warming time bomb…

--Dr. James E. Hansen


A publicly engaged scientist who upholds scientific evidence

At a congressional hearing in 1988, Dr. James Hansen, winner of 2018 Tang Prize in Sustainable Development, testified in front of the U.S. Senate Committee on Energy and Natural Resources, warning the world that human-made greenhouse effect would cause extreme weather, melting ice and rising sea levels. The next day, the headline of The New York Times read: “Global warming has begun.” Dr. Hansen’s admonition on that day was like an official clarion call to action on this impending crisis.  

Though the general consensus of opinion nowadays is that mankind has to exert itself to stem anthropogenic global warming, we need to briefly review its historical context to fully grasp the significance of Dr. Hansen’s testimony. For one thing, the Intergovernmental Panel on Climate Change (IPCC), a body of the United Nations that is responsible for the study and assessment of climate change, didn’t exist until 1998. For another, due to its own political stances and economic concerns, the American government has for a long time assumed a rather passive attitude toward climate change and chose to withdraw from the Kyoto Protocol in 2001, not to mention skeptics from all kinds of groups or fossil fuel companies who, motived by personal interests or believing in conspiracy theories, are either suspicious of or in denial of man-made climate change. All these incidents just further complicated discussions about curbing global warming by cutting carbon emissions.        

Once we know more about the factors at play here, we can see why the statement from Dr. Hansen that “the greenhouse effect has been detected, and it is changing our climate now” was an astonishing message delivered 30 years ago by an atmospheric and climate scientist. For their opinions to remain objective and accurate, scientists usually refrain from making comments with great certainty, but the certainty that characterized Dr. Hansen’s 1988 testimony was the result of not only the urgency of this issue but also the scientific proof he obtained after many years of research.

Around late 1970s and early 1980s, there have been ample evidence pointing to the correlation between the rapid increase in the concentration of atmospheric carbon dioxide and global warming, highlighting the urgent need for more research on this phenomenon. In 1981, Dr. Hansen together with other atmospheric physicists published a paper on the journal Science titled “Climate Impact of Increasing Atmospheric Carbon Dioxide,” analyzing how burning fossil fuels would affect our life. The argument covers both the short-term and long-term impact, and made several projections regarding future climate. This is the first research paper that laid out the consequences of anthropogenic global warming, including an increase in extreme weather events, threat to life and damages to property, all due to rising sea levels. Even when compared with the numerous research results published after Dr. Hansen’s paper came out, most of his predictions were surprisingly accurate. The fact that he has been relentlessly pursing the study of climate change since the 1980s shows the remarkable prescience he had 40 years ago.       

Dr. Hansen’s research efforts were not only intended to point out the problems, but, more importantly, they were meant to initiate our search for “solutions” to global warming.


Finding solutions, nonetheless, doesn’t mean we can rest assured that things will be “easier done than said,” even when we are dealing with severe climate crises that could lead to human extinction. On the one hand, for a long time, there has been an unbreakable tie between carbon emissions and the consumption of our primary source energy—fossil fuels. On the other, the successful implementation of plans such as revising current energy polices and developing renewable energies to substitute for fossil fuels does not happen overnight. Worried that recent updates to America’s energy policies cannot keep up with the pace of climate change, during the past few years, Dr. Hansen has been more actively appealing for public concerns about climate issues and for more effective actions,. He also floated the idea of a “carbon fee” which will raise the prices of fossil fuels and therefore discourage its consumption through this market mechanism. In addition, he didn’t shy away from public protests and has also tried to sway policy decision making by bringing his case to court.        

“What would you do if you knew what I know?” In his 2012 TED talk, this leading representative of climate activists put this question to his audience. 

While still a veteran member of NASA, Dr. Hansen was already on a trajectory quite different from other scientists. Before retiring from NASA, he had been under tremendous pressure from the US government who were irked by his statements on global warming. After retirement, he further raised his game, resorting to different measures, such as filing lawsuits against the US government, in order to force them to formulate new energy policies. His intention, nevertheless, is not different from that of other scientists: upholding scientific evidence that can bring forth a brighter future for human beings.

Other greenhouse gasses

If we want to have an informed discussion about the enhanced greenhouse effect, carbon emissions will only account for half of it. Other greenhouse gasses that should be taken into consideration include methane, nitrous oxide, CFC-12, HCFC-22, tetrafluoromethane, and so forth. Collectively, the damages they can do to the environment will not fall short of those inflicted by carbon dioxide. Prof. Veerabhadran Ramanathan, jointly awarded the prize in Sustainable Development, has taken an intense interest in the study of these “non-CO2” greenhouse gasses.   

The devil is in the details, so to speak. Though these substances are all defined as greenhouse gasses and they all absorb infrared radiation from Earth’s surface, they have different chemical formula, different atmospheric lifetimes and exert different impact. The greenhouse effect produced by each of these gasses can be illustrated by their global warming potential (GWP), “a measure of how much heat a greenhouse gas traps in the atmosphere up to a specific time horizon, relative to carbon dioxide.”[1] It depends on the atmospheric lifetime of a gas and is “evaluated over a specific timescale”[2] as shown below.

Gas name



Lifetime (years)

Global warming potential (GWP) for given time horizon




Carbon dioxide












Nitrous oxide









10 800

10 200

5 200




5 280

1 760




50 000

4 880

6 630

11 200



10 000

8 210

11 100

18 200

Sulfur hexafluoride


3 200

17 500

23 500

32 600

Nitrogen trifluoride



12 800

16 100

20 700


According to the table above, “over a 20-year period, one ton of methane has a global warming potential that is 84 times…greater than carbon dioxide,”[3] while the GWP of the fluorides listed at the bottom are thousands or even tens of thousands of times greater. What these gases lack “in volume” they make up “for potency.”[4] Another important factor in question here is the “atmospheric lifetime” of a gas (the length of time the greenhouse effect of a gas will last.) The longer its lifetime is, the greater its GWP will be over a longer span. Put simply, this measure tells us for how long the disaster a greenhouse gas causes will persist.  

Even for short-lived pollutants such as methane or CFC-12, the greenhouse effect created by the emission of one unit of any of them is still very unsettling. In other words, if we want to lessen the greenhouse effect rapidly, one of the highly efficient ways is to reduce the emissions of these non-CO2 greenhouse gases. Prof. Ramanathan, the first scientist to identify chlorofluorocarbons (CFCs) as greenhouse gases, should be credited with developing our understanding of the non-CO2 greenhouse gases. His further research then led to the discovery of black carbon, “a solid particle or aerosol, not a gas,” which “also contributes to warming of the atmosphere.”[5] 

Atmospheric black carbon is a component of an air pollutant known as particulate matter, or simply PM, an acronym many environmentally-minded people are very familiar with since terms like PM10、PM2.5 have become a new buzzword in recent years. PM is a generic term for particles suspended in the air due to the incomplete combustion of various compounds, such as coal. They can be found in factory smoke or are a byproduct of burning bituminous coal. In some areas, the black carbon emissions even exceed those of carbon dioxide. Fortunately, since it is short-lived, in theory, if we can properly implement a policy to reduce its emissions, we should be able to mitigate the greenhouse effect efficiently. Though this kind of pollutant can impose an extra burden on our body and our environment, it is relatively easy to execute plans to limit its emissions. For example, Prof. Ramanathan launched Project Surya with the mission of replacing traditional cook stoves with clean, energy-efficient cooking technologies in order to cut black carbon emissions, thereby improving the health of millions of people.      

After discovering the detrimental impact of the non-CO2 greenhouse gases, Prof. Ramanathan also attended the first meeting aimed at assessing the implications the non-CO2 pollutants have for our climate. His research findings have inspired the creation of “The Climate and Clean Air Coalition to Reduce Short-Lived Climate Pollutant,” with which 33 countries have already affiliated themselves.


It’s going to be a long-running battle to improve Earth’s atmosphere. Fortunately, the research works of these two scientists sounded an alarm that finally woke us up and gave us a window of opportunity to make amends with nature.


Social responsibilities that go hand-in-hand with fundamental scientific research

When Dr. Hansen and Prof. Ramanathan just set out on their journey to understanding climate science, atmospheric research and the study of man-made greenhouse effect were only in the embryonic stage. Hardly could anyone predict that research on climate change which at that time was generally assigned to the category of fundamental science and thus attracted scant attention would prove to be inextricably linked to our current lifestyles and the way we will live in the future. 

Besides the fruitful results yielded from their groundbreaking research, what should be accentuated more when it comes to the contributions of these two scientific scholars is how they were willing to leave the ivory tower of academia, making science accessible to general public and backing up their arguments with reliable statistics, so that environmental protection wouldn’t become another empty slogan. To realize a better and brighter future, we need scientific studies to steer us towards a more eco-friendly life as we pursue our own paths to a more sustainable world. 

Perhaps this is the best journey science can help us make.



“Global Greenhouse Gas Emissions Data,” United States Environmental Protection Agency, United States Government, September 2019, 4:40pm, https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data


“Global Warming Potential,” Wikipedia: The Free Encyclopedia, Wikimedia Foundation Inc., September 2019, 11:10 am, https://en.wikipedia.org/wiki/Global_warming_potential


“Greenhouse Gas,” Wikipedia: The Free Encyclopedia, Wikimedia Foundation Inc., September 2019, 11:00 am, https://en.wikipedia.org/wiki/Greenhouse_gas


“Methane Matters, Scientists Work to Quantify the Effects of a Potent Greenhouse Gas.” NASA Earth Observatory, NASA Goddard Space Flight Center, September 2019, 12:10 pm, https://earthobservatory.nasa.gov/features/MethaneMatters


[1] “Global Warming Potential.”

[2] Greenhous Gas.”

[3] “Methane Matters, Scientists Work to Quantify the Effects of a Potent Greenhouse Gas.”

[4] “Methane Matters, Scientists Work to Quantify the Effects of a Potent Greenhouse Gas.”

[5] “Global Greenhouse Gas Emissions Data”