A recent study in the journal Advances in Atmospheric Sciences reported that the heat absorbed in Earth’s oceans reached a new record in 2019. This has been the case for almost every year over the past decade, but this information dominated the news cycle this time with some particularly viral headlines noting that the amount of energy accumulating in the oceans is equivalent to detonating five Hiroshima atomic bombs per second, every second over the past 25 years.
While stunning, this isn’t a new analogy. After we published a paper about Earth’s energy accumulation in 2012, my colleagues and I at Skeptical Science created a website called 4Hiroshimas.com that provided a widget that websites can include on their homepages to illustrate the amount of heat accumulating on Earth as compared to the energy in the Hiroshima atomic bomb. The widget also uses other analogies to get the idea across, such as how the amount of heat accumulated compares to the energy in Hurricane Sandy, or 6.0 magnitude earthquakes, or Big Bens full of dynamite, or millions of lightning bolts.
Improved ocean heat measurements have since revised the rate of warming upwards from four to five ‘Hiros’ per second. (For the record, as of the writing of this article, our climate has accumulated the equivalent of a total of more than 2.8 billion Hiroshima bombs’ worth of heat since 1998.)Our team wasn’t the first to use this analogy. In 2010, oceanographer John Lyman compared the rate of ocean warming to atomic bombs, and James Hansen used the Hiroshima atomic bomb analogy in his February 2012 TED talk. One might say that the comparison has come under heat, however. Some criticize the analogy for exploiting or being insensitive to the horrors suffered by the people of Hiroshima. Others have complained that the analogy is imperfect, as all analogies are, by definition.On the other hand, the use of Hiros has one major upside. Earth and especially its oceans have been accumulating such a vast amount of heat due to human-caused global warming that it’s difficult to comprehend. Most people have little if any sense what 10 zettajoules per year—the amount of heat energy absorbed per year by the Earth—means. That’s why climate communicators have searched for a metric of comparison that the public can grasp. It’s relatively easy to visualize five atomic bombs detonating every second, and consequently comprehend the vast amount of energy being absorbed by the Earth’s climate system.
For those who nevertheless object to the Hiros analogy, perhaps microwaves offer a more palatable comparison. The heat accumulating in Earth’s oceans over the past 25 years is also equivalent to every person now on Earth running 35 standard household microwave ovens nonstop during Justin Bieber’s entire lifetime.
Critically, the rate of global heating is also accelerating. During the prior 25 years (1968–1992), the oceans only warmed at a rate equivalent to one Hiroshima bomb detonation per second, or 7.7 billion people each running 10 microwaves nonstop during that quarter-century period.
The good news: the rate at which we’ve been adding heat to Earth’s climate hasn’t changed much over the past two decades. The bad news: to avoid a potential climate catastrophe, global heating needs to begin declining soon and rapidly, which will require international implementation of numerous ambitious climate policies.
So far, many governments appear more inclined to keep increasing fossil fuel extraction than taking the necessary steps to slow global heating. Political leaders in many countries can implement these destructive policies without fear of losing power because too few people grasp the urgency of the climate crisis. Perhaps visualizing global heating as five atomic bomb detonations per second will help convey that sense of urgency to more people. Printable Version | Link to this page
Earth Loses 1.2 Trillion Tons of Ice Per Year, a Nearly 60% Increase From 1994
A pair of studies paint a worrying picture of accelerating ice loss around the world, with serious consequences for projections of sea level rise
Anew study finds that Earth lost 28 trillion tons of ice between 1994 and 2017, reports Chelsea Harvey for E&E News.
In a clear illustration of climate change’s worrying acceleration, the rate at which our planet is losing its ice skyrocketed from an average annual loss of roughly 760 billion tons of ice in the 1990s to more than 1.2 trillion tons per year in the 2010s, according to the study published this week in the journal Cryosphere.
Human activities, which have warmed our planet’s atmosphere and oceans by 0.47 degrees Fahrenheit and 0.22 degrees Fahrenheit per decade since the 1980, respectively, drove the massive ice loss.
This study’s staggering total of lost ice is the first global assessment that accounts for the Greenland and Antarctic ice sheets, Arctic and Antarctic sea ice, as well as ice lost from mountain glaciers the world over, according to E&E News. All told, the massive loss of ice has raised global sea levels by 1.3 inches since 1994.
“The ice sheets are now following the worst-case climate warming scenarios set out by the Intergovernmental Panel on Climate Change (IPCC),” says Thomas Slater, a climate researcher at the University of Leeds and the Cryosphere study’s lead author, in a statement. “Sea level rise on this scale will have very serious impacts on coastal communities this century.”
The IPCC’s estimates suggest that ice loss could raise sea level by up to 16 inches by 2100.
A second study, published earlier this month in the journal Science Advances, suggests that Earth’s ice loss is unlikely to stop accelerating, report Chris Mooney and Andrew Freeman for the Washington Post. The Science Advances paper finds 74 major ocean-terminating glaciers in Greenland are being weakened from beneath by intruding waters from warming seas.https://www.youtube.com/embed/0QVVzFPChAU
“It’s like cutting the feet off the glacier rather than melting the whole body,” Eric Rignot, a study co-author and a glacier researcher at NASA’s Jet Propulsion Laboratory and the University of California at Irvine, tells the Post. “You melt the feet and the body falls down, as opposed to melting the whole body.”
Speaking with the Post, Rignot says the study’s results suggest current estimates of sea level rise’s progression may be overly conservative. “As we peer below we realize these feedbacks are kicking in faster than we thought,” he says.
The worst-case scenario projected by the IPCC—the one that the Cryosphere study suggests Earth is currently tracking—might not actually be the worst-case scenario. Instead, ice loss and sea level rise could progress more rapidly than even the IPCC’s most pessimistic projections unless more is done to account for warm ocean water undercutting glaciers like the 74 in Greenland that the Science Advances paper identifies. Per the Post, the IPCC’s next report is expected later this year.
Drought is the sleeper weather story you’ll hear more about in 2021
Dry conditions are tightening their grip on the Southwest, including fire-prone Southern California
Drought is an insidious climate threat — by the time it has a hold of a region, impacts on ecosystems and water supplies can be locked in. It may not grab extreme weather headlines like the disrupted polar vortex or record hurricane season, but drought during 2020 and heading into 2021 is a looming story likely to grow in importance.
Intensity of drought
The above map shows drought conditions across North America, including parts of Canada and Mexico, valid on Dec. 10.
Nowhere is this more true than in the Southwest, population growth and years of drought conditions are putting the region on a collision course with drastic water management decisions. On Wall Street, traders can now bet on California water futures on commodity markets, enabling them to hedge against future scarcity, much as they trade gold, oil and agricultural products.
The forecast persistence of La Niña, a periodic cooling of the waters in the eastern tropical Pacific along the equator, through the winter favors a worsening of drought conditions along the southern tier of the U.S.
Sea-surface temperature anomaly, December 2020
Difference from 1981-2010 average
In Southern California, the wildfire season finally came to an end in late December, but rains have been sporadic and light into the start of the new year. The state’s first snow survey of the year shows that the statewide snowpack was just 52 percent of average on Jan. 1. Storms are likely to increase that percentage during the next few weeks, but the dry fall has put the Golden State at a deficit that could be difficult to make up given the favored storm track.
Unlike El Niño years, which feature above average water temperatures in the tropical Pacific and can direct a relentless firehose of moisture at the West throughout the winter, La Niña winters tend to favor stormy conditions in the Pacific Northwest instead.
A total of 49 percent of the Lower 48 states were in moderate to exceptional drought conditions as of Dec. 29, with dry conditions extending north into Alberta.
Continental U.S. drought conditions
80% of total land area
While droughts come and go, there is increasing evidence that parts of the U.S., namely the Southwest, are enduring long-term “megadrought” conditions seen in historical tree ring records. This is partly related to climate change, which worsens droughts by increasing temperatures, thereby turbocharging the loss of moisture from plants and soils. Climate change is also shifting weather patterns in ways that favor drier conditions in the Southwest U.S., pushing storm tracks northward.
The above chart shows the percent of total land area in the Lower 48 states that are in drought conditions. You’ll see the huge spike between 2010 and 2015, which coincided with a costly drought in Texas and California’s most intense and long-lasting drought more in than a millennium, and the recent climb that has not yet leveled off.
Probability of precipitation
The seasonal precipitation forecast from the Climate Prediction Center at NOAA shows the likelihood of a La Niña-tinged winter weather pattern, with a drier than average southern tier. This would be especially bad news for states like California, New Mexico and Arizona, but also southern Texas and Florida, too.
About this story
North America drought data sourced from National Centers for Environmental Information’s North American Drought Monitor (released on Dec. 10). U.S. precipitation outlook data issued on Oct. 15 by NWS Climate Prediction Center. U.S. drought time series data as of Dec. 29, 2020.
Lauren Tierney contributed to this report.