Global temperatures before and after Dr. James Hansen's Senate testimony on 23 June 1988, showing two periods, 1959—1988 and 1988—2017. Graphic: Harry Stevens / Axios

By Harry Stevens
23 June 2018

(Axios) – Three decades have passed since then-NASA scientist James Hansen testified before the Senate Energy committee and alerted the country to the arrival of global warming.

Why it matters: The predictions of the world's leading climate scientists have come true, with dire consequence for the planet.

  • In the 30-year period prior to Hansen’s testimony, the Earth’s surface was, on average, less than 0.2°F warmer than the 20th-century average. In the 30 years since, the planet’s surface has, on average, undergone a six-fold temperature increase.
  • Hansen's temperature projections weren't exactly on target, since he projected a slightly higher amount of warming than what has occurred, but about two-dozen climate scientists told Axios that overall, his main conclusions were right.

In his 23 June 1988 testimony, Hansen made three key points:

  1. The Earth has gotten warmer.
  2. So warm, in fact, that the temperature trend was almost certainly due to the greenhouse effect, which is enhanced by emissions of gases like carbon dioxide and methane from burning fossil fuels.
  3. As a result, summer heat waves and other extreme weather events will become more common.

"The greenhouse effect has been detected, and it is changing our climate now,” Hansen said. When he spoke, 1988 was on track to become the hottest year of all-time. Since then, that record has been broken six more times – in 1990, 1998, 2010, 2014, 2015, and 2016.

  • In an interview with the Guardian this week, Hansen gave a bleak assessment of the last thirty years. “All we’ve done is agree there’s a problem,” he said. “We haven’t acknowledged what is required to solve it.” [more]

Special report: A 30-year alarm on the reality of climate change

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