Climate Predictions: How are We Doing?
August 19, 2016
I’ve been waiting for this.
Above, Zeke Hausfather of the Berkeley Earth Surface Temperature project tweeted an updated comparison of global temps to model predictions, including the most recent measurements.
In 1981 James Hansen and colleagues published research in the prestigious peer-reviewed journal Science titled “Climate Impact of Increasing Atmospheric Carbon Dioxide.” They discussed the result of basic physics, that carbon dioxide in the air inhibits Earth cooling off, thus heating the planet. They also reported the results of computer simulations of Earth’s climate in a world with ever-increasing CO2.
In that research they stated some of the more notable results, both for the long term (if we double the amount of CO2 in the air), and some of the changes expected by the year 2010 if CO2 kept increasing the way it had been (because of our burning fossil fuels). These include:
- Doubling the atmosphere’s CO2 would raise Earth’s overall temperature by 2.8°C (5°F).
- By 2010, Earth’s temperature would rise about 0.4°C (0.7°F).
- The Arctic will warm considerably faster than the globe as a whole.
- There will be a reduction of sea ice in the Arctic.
- There’s a chance we might see the opening of the fabled “Northwest passage” during late summer.
Naturally one wonders, how did things turn out?
Worth reading the original, but obviously, as Zeke Hausfather’s graph shows at the top of the page, temperature predictions have been on the money, despite howls and obfuscation from climate deniers any time there is not a monotonic year-on-year rise.
But that’s not all..
They also predicted that the Arctic would warm faster than the planet as a whole. NASA also reports the temperature for various regions of the Earth, and here’s a comparison of the warming since 1970 for the globe as a whole in blue, to that for the Arctic (in this case, the Earth north of latitude 64°N) in red:
The Arctic has indeed warmed faster than the global average, by a lot. Since 1970, it has warmed nearly three times as fast.
What about their projected decline of Arctic sea ice? Here’s the annual average extent of Arctic sea ice since we started observing with satellites in the late 1970s (data from the National Snow and Ice Data Center, with a trend line in red):
Finally, what about the Northwest passage? There is no single specific “Northwest passage,” it’s a generic term for crossing between the Atlantic and the Pacific oceans by sailing over the northern part of North America. It has been attempted many times, and was finally accomplished when Roald Amundsen reached Alaska via that route in 1906. But by no means was it smooth sailing; departing in 1903 it took him three years, including winters being frozen into the ice.
What is really meant, in practical terms, is just that smooth sailing which would enable passenger and cargo ships to make the journey — without having to take three years to do it. Because of global warming, it has already happened. On this very day, a cruise ship called “Crystal Serenity” is departing Alaska with over 1,000 passengers, bound for New York with a scheduled passage by Greenland. It has real risks, and I wish them a safe journey, but there’s also no getting around the fact that the prediction that we might see the Northwest passage actually practical during summer is no longer a dream or a slogan, it’s a reality.