Want to Understand This Summer's Heat? Imagine 800,000 Hiroshima Atom Bombs Exploding Every Day

That unimaginable amount of energy is why July was the hottest month on record, and why 2023 may rank as warmest year.

ImaGeo iconImaGeoBy Tom YulsmanAug 17, 2023 6:45 PM
Trinity Atom Bomb Test
The first atomic bomb was exploded at the Trinity test site on July 16, 1945 at 5:29:45 a.m. This photo shows the explosion at just .025 milliseconds into the blast. The explosive yield was equivalent to 21,000 tons of TNT. To learn about the connection between atom bombs and global heating, see the story below. (Credit: U.S. Dept. of Defense. Colorization of original black and white photo by Tom Yulsman)


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You likely don't need me to tell you that in most places, July was frightfully warm. But compared to previous July's, just how bad was it?

An analysis released by NASA has just answered this question: Last month was unlike any of the previous 1,716 months in the agency's climate records. And it wan't even close.

“This July was not just warmer than any previous July – it was the warmest month in our record, which goes back to 1880," says Gavin Schmidt, director of NASA's Goddard Institute for Space Studies, or GISS.

Global temperature anomalies for every July since the 1880s, based on NASA's GISTEMP analysis. Anomalies reflect how much the global temperature was above or below the 1951-1980 norm for July. (Credit: NASA’s Goddard Institute for Space Studies)

NOAA's independent assessment found essentially the same thing. As the agency put it in a release, "Earth just roasted under its hottest July on record," and it was likely the warmest month ever.

By NOAA's reckoning, last month also was the 47th consecutive July, and 533rd-consecutive month, with temperatures at least nominally above the 20th-century average. The agency's records go back even further than NASA's, to 1849.

In case you're wondering, that's a timespan of 2,088 months.

Sizzling Seas

July also was the fourth-consecutive month that the global ocean surface temperature hit a record high, according to NOAA. And those record highs have been continuing.

Ocean warming has been getting a boost from El Niño conditions that emerged in June. Those conditions now stand a 95 percent chance of continuing through Northern Hemisphere winter, and a two in three chance of blossoming into a strong El Niño.

With long-term, human-caused global heating getting a continuing boost in coming months from El Niño, there's now a nearly 50 percent probability that 2023 will rank as the warmest year on record, according to NOAA.

Global surface temperature anomalies for July 2023 according to NASA-GISS. Temperature anomalies reflect how July 2023 compared to the average July temperature from 1951-1980. (Credit: NASA’s Goddard Institute for Space Studies)

“The science is clear this isn’t normal," NASA's Gavin Schmidt says. "Alarming warming around the world is driven primarily by human-caused greenhouse gas emissions."

Earth's Energy Imbalance Measured in Atom Bombs

Former NASA-GISS director James Hansen has played a key role in alerting humanity to risks posed by those emissions, dating all the way back to the 1980s. Now serving as director of Climate Science, Awareness and Solutions at Columbia University, Hansen cuts through the fog of climate science complexity by focusing on how we have thrown the energy balance of our planet out of whack. As he put it in a TED Talk in 2012:

"Adding CO2 to the air is like throwing another blanket on the bed. It reduces Earth's heat radiation to space, so there's a temporary energy imbalance. More energy is coming in than going out, until Earth warms up enough to again radiate to space as much energy as it absorbs from the Sun."

Back when he gave that TED Talk, Hansen noted that this energy imbalance was about six-tenths of a watt per square meter. "That may not sound like much, but when added up over the whole world, it's enormous," he said. 

Since then, the energy imbalance has only grown bigger: Research has revealed that from mid-2005 to mid-2019, it has roughly doubled.

To fully grasp what that means, consider this: Before that doubling, Hansen estimated that the energy building up in Earth's climate system was equivalent to exploding 400,000 Hiroshima atomic bombs per day, 365 days per year.

Now, with a rough doubling in the imbalance, we're sprinting toward a million atom bombs of energy accumulating each and every day.

Earth's seas continue to sizzle: In records dating back more than four decades, sea surface temperatures outside of the polar regions have been running far higher than ever seen before. (Credit: Climate Reanalyzer)

Most of that energy is being absorbed by the oceans. So the record ocean warmth we've been experiencing shouldn't come as any surprise. And what goes into the ocean doesn't stay in the ocean. The heat doesn't simply vanish.

All those atom bombs worth of energy are contributing greatly to the melting of sea ice and ice shelves, which in turn is helping to reinforce global heating through the ice-albedo feedback phenomenon. Moreover, accumulating ocean heat exacerbates sea level rise by causing water to expand. It also evaporates water, contributing to storminess. And it directly reheats the atmosphere, which, of course, makes heat waves worse — and helps to push up the overall rising trend of global surface temperatures.

Unfortunately, heat absorbed in the oceans can warm Earth for decades after it was absorbed.

Climate Change is Still a Solvable Crisis

In his forthcoming book, "Our Fragile Moment", University of Pennsylvania climate scientist Michael Mann observes that "the concentration of carbon dioxide in the atmosphere today is the highest since early hominids first hunted on the African savannas. It is already outside the range during which our civilization arose. If we continue to burn fossil fuels, it is likely that the planet will warm beyond the limit of our collective adaptive capacity. How close are we to the edge?"

You'll need to read his excellent book to find out how he answers that question. But right at the beginning, he goes out of his way to try to counteract despair, writing that "the study of Earth's history betrays some degree of climate resilience. Climate change is a crisis, but a solvable crisis."

In a recent newsletter, James Hansen and a colleague agreed. While noting that we "are entering a new climate frontier," they also said this "does not mean that the problem is unsolvable. It is possible to restore Earth’s energy balance." They go on to say that maybe when people find climatic conditions "sufficiently disagreeable, we can begin to consider the actions needed to restore a propitious climate."

Thanks to brutal heat waves, devastating deluges, and other impacts, the climate has been especially disagreeable since the start of this year. And with a growing El Niño, there's every reason to think this will continue through the end of the year.

But will conditions finally seem disagreeable enough to spark greater action?

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