James Edward Hansen, born on March 29, 1941, is an American climatologist. He works as a part-time professor and leads the Program on Climate Science, Awareness and Solutions at the Earth Institute of Columbia University. He is most recognized for his research on climate change, his 1988 testimony to the U.S. Congress that increased public understanding of global warming, and his efforts to encourage actions to prevent severe climate change. In recent years, he has taken part in climate activism to reduce the impacts of global warming, which has led to his arrest on some occasions.

In 2000, Hansen suggested a plan to address global warming by focusing on reducing greenhouse gases that are not carbon dioxide, such as methane. His studies showed that these gases contributed more to observed global warming than carbon dioxide. However, he noted that if carbon dioxide emissions continued to increase, it would become the main cause of climate change.

Early life and education

Hansen was born in Denison, Iowa, to James Ivan Hansen and Gladys Ray Hansen. He learned physics and astronomy in the space science program of James Van Allen at the University of Iowa. He got a B.A. in physics and mathematics with top honors in 1963, an M.S. in astronomy in 1965, and a Ph.D. in physics in 1967, all from the University of Iowa. He took part in the NASA graduate traineeship from 1962 to 1966. During 1965 to 1966, he was a visiting student at the Institute of Astrophysics at Kyoto University and in the astronomy department at the University of Tokyo. In 1967, he started working at the Goddard Institute for Space Studies.

Career

After graduate school, Hansen continued his research on radiative transfer models to study the atmosphere of Venus. He later used and improved these models to learn more about Earth's atmosphere, especially how aerosols and trace gases affect Earth's climate. His work with global climate models has helped scientists better understand Earth's climate. In 2009, his first book, Storms of My Grandchildren, was published. In 2012, he gave a TED Talk titled "Why I Must Speak Out About Climate Change."

From 1981 to 2013, Hansen was the director of the NASA Goddard Institute for Space Studies in New York City, which is part of the Goddard Space Flight Center.

As of 2014, Hansen leads the Program on Climate Science, Awareness, and Solutions at Columbia University's Earth Institute. The program aims to link scientific research on climate change with efforts to raise public awareness and support policies that address climate issues.

Hansen represented his granddaughter and "future generations" as plaintiffs in the Juliana v. United States lawsuit, which challenged the U.S. government and some of its executive branch actions for failing to protect a stable climate system. The case did not succeed.

Research and publications

At the University of Iowa, Hansen became interested in science and the research conducted by James Van Allen's space science program in the physics and astronomy department. A decade later, his focus changed to studying how changes in Earth's atmosphere caused by human activities might affect the planet's climate.

Hansen has studied how heat moves through planetary atmospheres, especially how satellites observe Earth's atmosphere and surface from space. Satellites can monitor the entire planet, making them valuable tools for studying global changes. He also works on creating models to understand climate trends and how human activities influence the climate.

In the late 1960s and early 1970s, after completing his Ph.D., Hansen published research on Venus. Venus has a high temperature in radio waves compared to infrared light. He suggested that Venus's hot surface was caused by particles trapping the planet's internal heat. Later studies showed that Venus's atmosphere was once more like Earth's, with liquid water on its surface, but a runaway greenhouse effect caused by water evaporation led to high levels of greenhouse gases.

Hansen studied the composition of Venus's clouds. He compared how ice clouds reflect near-infrared light to observations of Venus and found they matched. He also used a model to estimate the size of ice particles if the clouds were made of ice.

By 1974, scientists had not yet determined the composition of Venus's clouds, with many suggesting possible materials like water or other compounds. Hansen and Hovenier used how sunlight reflects from Venus to show that the clouds were spherical and had specific properties that ruled out all proposed materials except sulfuric acid. Later research confirmed that Venus's clouds are a thin haze and sulfuric acid droplets.

The Pioneer Venus project launched in 1978. Hansen and colleagues studied how clouds in the ultraviolet spectrum changed. They found three types of cloud materials: a thin haze, sulfuric acid clouds, and an unknown substance below the sulfuric acid layer. Data from the mission confirmed that low- and mid-level clouds are sulfuric acid with a size of about 1 micrometer, while a haze layer exists above the clouds. Studies in the 1980s showed that Venus's clouds are mainly sulfur dioxide and sulfuric acid droplets.

In 1981, the first global temperature analysis by NASA Goddard Institute for Space Studies (GISS) was published. Hansen and his co-author studied temperature data from 1880 to 1985. They found that temperatures in regions close to each other were similar, allowing scientists to combine data for long-term trends. They concluded that global temperatures could be measured even if most weather stations were in the Northern Hemisphere. They found that temperatures had risen by 0.5-0.7 °C over the past century, with similar warming in both hemispheres. In 1988, the four warmest years on record were in the 1980s. Hansen stated that Earth was warmer than at any time in recorded history, linked to the greenhouse effect, and that extreme weather was becoming more likely.

After the 1991 eruption of Mount Pinatubo, global temperatures cooled in 1992. Some scientists thought this might lead to cooler years, but Hansen argued that understanding climate physics, not just temperature data, was key.

In 1999, data showed that 1998 was the warmest year since 1880, with faster warming than ever recorded. The El Niño event in 1998 did not fully explain the temperature rise. In the U.S., warming was less noticeable, and some areas even cooled slightly.

In 2001, temperature calculations were updated to correct for issues like time-of-observation bias, changes in weather station locations, and differences between urban and rural areas. Studies showed that urban areas had warmer temperatures due to local factors.

The high 1998 temperatures from El Niño led to a short cooling period, but Hansen's 2001 report confirmed that global warming continued. By 2006, temperatures were 0.8 °C warmer than a century earlier, and scientists concluded that recent warming was real and not caused by urban heat islands. More warming occurred in higher latitudes, supporting the idea that human activities caused the changes.

In 2007, Stephen McIntyre pointed out a problem with U.S. temperature data from the 2000s. NASA corrected the data and thanked McIntyre for the discovery. Hansen said some news outlets overreacted to the issue. In 2010, Hansen published a paper on current global temperature analysis.

Hansen also studied how black carbon affects regional climates. In China, northern areas have seen more droughts, while southern areas have had more summer rain and floods. Southern China has cooled slightly, while the rest of the world has warmed. Research with Menon and others showed that black carbon heats the air, increases rainfall, and causes more surface cooling than sulfates.

In 2011, Hansen and colleagues published a study on how black carbon influences climate patterns in Asia.

Analysis of climate change causation

The first step people should take is to use the democratic process. What is troubling many people, including me, is that actions taken through democracy can influence elections, but political leaders often respond with false promises about environmental efforts.

Hansen explained that when determining who is responsible for climate change, the impact of greenhouse gas emissions depends not on current emissions, but on the total emissions over time as these gases remain in the atmosphere.

According to this measure, as of 2009, the United Kingdom had the highest total emissions per person among major economies, followed by the United States and Germany. This is true even though China currently produces the most greenhouse gases each year.

Regarding public policy, Hansen criticized efforts he believes mislead people about climate change. He specifically mentioned commercials by the Competitive Enterprise Institute with the message "carbon dioxide—they call it pollution, we call it life," and politicians who accept money from fossil-fuel companies and claim global warming is "a great hoax." Hansen also stated that steps to reduce global warming do not require hardship or lower quality of life. Instead, these steps can lead to benefits such as cleaner air and water, and the growth of high-tech industries. He criticized the climate change policies of both the Clinton and George W. Bush Administrations. In a 2009 interview, Hansen said, "We cannot now afford to delay change. We must take a new path under the new administration. Obama had four years to lead the way and set an example for the world. America must take the lead."

Climate change activism

In 1988, Hansen was invited by Rafe Pomerance to speak to the United States Senate Committee on Energy and Natural Resources. During his testimony, Hansen stated that global warming has reached a level where scientists can confidently link it to the greenhouse effect, which is already changing the climate. He said NASA was 99% certain that the warming was caused by greenhouse gases in the atmosphere, not random changes.

According to science historian Spencer R. Weart, Hansen's testimony helped more people understand climate change. Richard Besel of California Polytechnic State University said Hansen's testimony was an important turning point in the history of global climate change. Timothy M. O'Donnell of the University of Mary Washington called it "pivotal," saying it started public discussions about global warming and turned the topic into a policy debate. Roger A. Pielke of the National Center for Atmospheric Research said Hansen's "call to action" brought global warming and its effects, like more hurricanes and heat waves, into the public eye.

Hansen has criticized the coal industry, saying it produces the most carbon dioxide from human activities. He has called for ending coal power completely by 2030.

In 2007, during a testimony before the Iowa Utilities Board, Hansen compared coal trains to "death trains" and said they were "no less gruesome than if they were boxcars headed to crematoria, loaded with uncountable irreplaceable species." The National Mining Association said this comparison "trivialized the suffering of millions" and hurt Hansen's credibility. Hansen later apologized, saying he did not mean to cause pain and regretted his words.

On June 23, 2009, James Hansen and 30 others, including actress Daryl Hannah, were arrested for blocking traffic during a protest against mountaintop removal mining in West Virginia. The protesters tried to enter Massey Energy Company's property but were stopped by coal miners and supporters. Hansen said mountaintop removal mining should be abolished and urged President Barack Obama to take action.

After his arrest, New York Times columnist Andrew Revkin said Hansen had gone beyond the usual role of scientists in environmental debates.

In September 2010, Hansen and about 100 others were arrested near the White House, seeking a ban on mountaintop removal or surface mining.

In 2009, Hansen opposed cap and trade, instead supporting a carbon tax that would return collected money equally to citizens. He has promoted this idea through the Citizens' Climate Lobby.

Hansen retired from NASA in April 2013 after 46 years of service, saying he would focus more on political and legal efforts to reduce greenhouse gases. That same month, the National Center for Science Education named him an advisor to help teach climate change in schools.

In 2013, Hansen opposed the Keystone pipeline, which would carry oil from Canada's Athabasca Oil Sands. He said oil sands and tar shale produce more carbon than regular oil and should not be used as energy sources. He urged President Obama to reject the pipeline. On February 13, 2013, Hansen was arrested again at the White House with Daryl Hannah and Robert F. Kennedy, Jr., during a protest against the pipeline.

Hansen supports a system where a fee on carbon emissions is returned equally to all U.S. residents. He said this would make fossil fuels like tar sands too expensive to use and help the economy. In an interview in 2015, he explained that putting a price on carbon would make the costs of fossil fuels honest and help the environment.

At the end of 2008, Hansen listed five priorities for President-elect Barack Obama: using energy efficiently, developing renewable energy, creating a smart grid, building advanced nuclear reactors, and using carbon capture and storage. He opposed the Yucca Mountain nuclear waste repository, saying the money saved should fund new nuclear technologies.

In 2009, Hansen wrote an open letter to President Obama, calling for a ban on coal plants that do not capture and store carbon dioxide. In his book Storms of My Grandchildren, he discusses his Declaration of Stewardship, which includes a principle to rethink how humans use Earth's resources.

Honors and awards

James Hansen was elected to the National Academy of Sciences in 1996 for his work in creating early models that help scientists understand how energy moves through the atmosphere and how planets' atmospheres behave. He also developed simple and complex models to study Earth's climate, explained how climate changes are caused by natural and human activities, analyzed climate trends using real-world data, and predicted how human actions might affect Earth's climate. In 2001, he received the Heinz Award in the Environment, which included a prize of $250,000, for his research on global warming. In 2006, he was listed by Time magazine as one of the 100 Most Influential People. That same year, the American Association for the Advancement of Science (AAAS) honored him with the Award for Scientific Freedom and Responsibility for his efforts to encourage scientists to share their findings openly on important public issues.

In 2007, Hansen shared a $1-million Dan David Prize for his work that had a major impact on science, technology, culture, or society. In 2008, he received the PNC Bank Common Wealth Award of Distinguished Service for his achievements in science. At the end of 2008, he was named Scientist Communicator of the Year by EarthSky Communications and a group of 600 scientists for his clear communication about climate change.

In 2009, Hansen was awarded the Carl-Gustaf Rossby Research Medal, the highest honor from the American Meteorological Society, for his contributions to climate modeling, understanding climate change, and sharing climate science with the public.

Andrew Freedman wrote in The Washington Post that the society made a mistake by giving the medal to Hansen. He said the issue was not his work, but the recognition of his public communication on climate change.

In 2010, Hansen won the Sophie Prize, created by Norwegian author Jostein Gaarder, for his role in helping people understand how human activities cause climate change. In 2012, Foreign Policy named him one of its Top 100 Global Thinkers for his early warnings about climate change. That same year, he received the Commonwealth Club of California's Stephen H. Schneider Award for Outstanding Climate Science Communications in San Francisco.

In 2013, Hansen received the Joseph Priestley Award at Dickinson College for his work on climate change, including using early computer models to study climate trends and connect scientific knowledge to climate policy. He gave a lecture titled "White House Arrest and the Climate Crisis" that day.

In 2016, Hansen was a co-winner of the BBVA Foundation Frontiers of Knowledge Award in the Climate Change category. He and climatologist Syukuro Manabe were recognized for creating the first computer models that could simulate climate behavior. These models accurately predicted how Earth's temperature would rise due to increasing carbon dioxide in the atmosphere. Many modern climate models are based on their work.

In June 2018, Hansen was named a joint winner of Taiwan's Tang Prize with scientist Veerabhadran Ramanathan. His share of the prize was worth NT$25 million.

Publications

James Hansen has written more than 160 articles. Since 2020, he has shared observations and opinions on the website redgreenandblue.org, posting about once each month.

• Hansen, James E. (2009). Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity. New York: Bloomsbury Publishing. ISBN 978-1-60819-200-7.