James Hansen: scientist turned environmental activist


For thirty years, the NASA climatologist has been working on our Earth’s climate, how it has changed and the causes of these changes. He has proved that mankind bears significant responsibility, and strongly advocates action that will curb the process.


In February 2012, James Hansen gave a TED talk entitled “Why I must speak out about climate change.” He wore a pair of jeans, a Ralph Lauren shirt and a cow-boy hat on his head: the NASA scientist looked like an incarnation of the American spirit. And he warned:

Imagine a giant asteroid on a direct collision course with Earth. That is the equivalent of what we face now [with climate change], yet we dither.

James Hansen is a climatologist, an expert in planetary atmospheres (particularly those of Venus and the Earth) and the director of the Goddard Institute for Space Studies (GISS) at NASA. For the past thirty years, he has been studying the climate changes occurring on the surface of the Earth and the human-caused forces on these changes. This scientific work has led him to become an activist for action to curb climate change. “What would you do if you knew what I know?” said Hansen in front of the TED audience. Become activists too?

From astronomy to ecology


James Hansen is first and foremost a scientist. He studied under the patronage of James Van Allen at the University of Iowa, in the physics and astronomy department, and then started to work on Venus’ atmosphere. In the 1970s, evidence was starting to be found that, billions of years ago, Venus had experienced a greenhouse effect that led it to become very hot, and enveloped by an atmosphere composed of carbon dioxide and by a smog of sulphuric acid. This led Hansen, who had already joined NASA where he participated in the work on Venus, to focus on the greenhouse effect that was occurring on Earth and, more particularly, on the anthropogenic causes of this greenhouse effect. He developed global climate models that helped develop a better understanding of the Earth’s climate and monitor its changes. In 1981, the first GISS global temperature analysis was published. It was updated in 1988 and found that the four warmest years on record (that is since 1880) were all in the 1980s. That year, Hansen gave an infamous speech in front of the American Congress to warn that “global warming had begun.” In 1999, the study established that 1998 had been the warmest year ever recorded, and that the rate of temperature change was higher than ever. Hansen and his teams also worked on the origins of the phenomenon, quickly ruling out natural events (like volcanic eruptions) as the sole causes. In 2003, in Can We Defuse the Global Warming Time Bomb? Hansen explicitly stated that the anthropogenic impacts on climate were now greater than the natural causes. He thus advocated for active measures:

halting global warming requires urgent, unprecedented international cooperation, but the needed actions are feasible and have additional benefits for human health, agriculture and the environment.

The conviction that something had to be done urgently led him to become an activist – and to enter the field of polemic. Aside from his several arrests, the scientist drew public attention when he made thunderous statements: he criticised politicians for being funded by fossil-fuel interests and then calling global warming a hoax, compared coal trains to death trains “loaded with uncountable irreplaceable species” and called for fossil-fuel company executives to be put on trial for “high crimes against humanity and nature”, for trying to misinform on global warming. This position has brought him a lot of criticism (physicist Freeman Dyson said in 2009 that “Hansen had turned his science into ideology”), but also recognition from the general public and environmental activists. At the end of the day, his political commitment has brought him more fame than his scientific work – and has helped bring the issue he cares about most to the front of the stage.

(Photo by Josh Lopez http://commons.wikimedia.org)