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What's the rate of global warming?
400,000 Hiroshima A-bombs a day

by Joe Romm


Conveying abstract, hard-to-visualize ideas is a challenge
That’s a core reason why the best communicators have always used metaphors. As Aristotle wrote in his classic work Poetics,

“The greatest thing by far is to be a master of metaphor.”

How can we convey the Earth’s staggering rate of heat build up from human-caused global warming — 250 trillion Watts (Joules per second)? The analogy to the energy released by the Hiroshima bomb has been used in recent years by a number of scientists, such as NOAA oceanographer John LymanMike Sandiford, Director of the Melbourne Energy Institute and NASA climatologist Jim Hansen. In his TED talk Hansen explains that the current rate of increase in global warming is:

“Equivalent to exploding 400,000 Hiroshima atomic bombs per day, 365 days per year. That’s how much extra energy Earth is gaining each day.”

That comes out to more than four Hiroshima bombs a second, which is a metric Skeptical Science has turned into the widget above. I prefer the 400,000 Hiroshimas per day metric simply because the heat imbalance is occurring over a very large area, which four Hiroshimas don’t do justice to.

The deniers don’t like the metaphor because, they assert, it is inexact and sensationalistic. But the deniers don’t like the literal facts because they think those are inexact and sensationalistic, too, so we can safely ignore them.

Metaphors are not literal — by design
If you don’t like non-literal comparisons, you won’t like metaphors. I have argued at great length that one of the major failings of science communication is the failure to use figurative language. For what it’s worth, Aristotle believed,

“To be a master of metaphor is a sign of genius, since a good metaphor implies intuitive perception of the similarity in dissimilars.”

So I’ve been delighted to see scientists start to use metaphors, such as analogizing the effect of greenhouse gases on extreme weather, by saying it’s like the climate on steroids. But of course the climate isn’t literally on steroids. It is figuratively on steroids. It is literally on CO2, which is much worse.
Ironically, metaphor is the source of some of the most common terms in climate science: the greenhouse effect and greenhouse gases. Ultimately, metaphors need to be judged for whether they bring more light than heat, as it were.

The assertion that “climate change is nothing like atom bombs” isn’t quite true. Like global warming, atom bombs deliver a vast amount of energy in a very short period of time, which is the primary point of the metaphor. Indeed, when the first nuclear explosion in history occurred in July 1945, one observer said the fireball “rose from the desert like a second sun.”  Again, climate change and atoms bombs are man-made — and highly destructive. Like Frankenstein’s monster, both have become symbols of how our mastery of science and technology has had unintended consequences. The scientific community has issued warning after warning about the dangers of both an unrestricted nuclear arms race and unrestricted CO2 emissions — warnings that have been largely ignored for decades.

So this is a worthwhile metaphor
The Hiroshima bomb does have an element that goes beyond most nuclear bombs because it was dropped on a city and killed some 100,000 people. But is the metaphor flawed because the association of death and destruction is also easy to grasp”?

One of the whole points of the metaphor is that “puny humans” can in fact inflict catastrophic damage through human-caused global warming. On our current emissions path, Sandy-type storm surges will be an every year phenomenon for the New Jersey coast of America in a half-century! And then we have the warning of Harold Wanless, chair of University of Miami’s geological sciences:

“Miami, as we know it today, is doomed. It’s not a question of if. It’s a question of when.”

Like the Hiroshima bomb, global warming is capable of destroying cities. So the “association of destruction” of the metaphor isn’t a bug, it’s a feature. Assuming we don’t end our self-destructive carbon feeding frenzy anytime soon, I do not think future generations will think this aspect of the metaphor is in the least bit flawed.

While global warming doesn’t kill tens of thousands of people in a flash, it is on track to reduce the carrying capacity of the planet post-2050 far below the 9 billion people that we are projected to have.

Again, where we are headed, I doubt future generations will think this aspect of the metaphor was morally inappropriate. It’ll be our inaction — and everyone and everything that fed our inaction — that will be seen as morally inappropriate.

I do understand metaphors are not for everyone, but I do think that they are the perhaps the defining figure of speech of history’s greatest communicators. And as metaphors go, the Hiroshima bomb one seems to be better than most.

Aristotle would be proud.

◊  In a world where disinformation is a norm, Dr Joe Romm is a voice of
Publ. here 25.12.2013.

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