Blue Marble

You Might Be Cold Right Now, But Your Planet Isn't

| Wed Jan. 29, 2014 7:00 AM EST
Snow in Georgia from Winter Storm Leon

This week, the Central, Southern, and Eastern United States have all experienced yet another bout of frigid cold and snow, one that left motorists in the Atlanta area stranded in their cars overnight. Freezing air from the Arctic has been an all too frequent visitor this month, and with this latest arrival we've seen record-low daily temperatures for Detroit (minus-9 degrees), Grand Rapids, Michigan (minus-9 degrees), and Lubbock, Texas (7 degrees), among other locations, according to Weather Underground.

There's no denying that it's cold out; and once again, that's prompting anecdotal claims that somehow, global warming is in question. Yet it's important to bear in mind that just because you're freezing—or even have seen a new daily record-low temperature in the particular place where you live—that doesn't mean that what's happening to you accurately reflects what's happening to the planet overall, or even to the United States.

In other words, don't be the white-capped guy in this XKCD comic:

So how do you avoid this particularly annoying kind of weather-induced cluelessness? Rather than thinking with your gut about cold temperatures, try thinking with your (or, science's) statistics.

Consider: If global warming is not happening, then scientists say that the planet ought to be breaking just as many hot temperature records as cold temperature records overall. In a warming climate, however, you would naturally break more hot records than cold records over time. So what kind of climate do we live in?

According to data from the National Climatic Data Center (NCDC), the United States has set 1,347 daily low temperature records so far in January 2014, and tied another 304, for a total of 1,651. (A daily record refers to the highest or lowest temperature recorded in a particular place on a particular day of the year, as opposed to an all-time record, which is the highest or lowest temperature ever recorded in that place on any day.) When it comes to daily highs, by contrast, there have been only 489 new records and 237 tied records (many of them in the West and in Alaska), for a total of 726. (These records are updated regularly; our results are based on a search conducted yesterday evening.)

So based on just this month alone, record lows are indeed outpacing record highs. The data are clear: We've had a very cold month.

Yet if you zoom out and examine the long-term trend, things look different. In a 2009 paper in the journal Geophysical Research Letters, for instance, a team of climate and weather researchers analyzed the ratio of daily hot records to daily cold records from 1950 to 2006, with a careful sampling of overall weather station data. The result? They found that the ratio of hot records to cold records has been rising since the 1970s, and by the 2000s stood at about 2-to-1. That's precisely what you'd expect to see if global warming is happening. Here's a visualization of their results:

Ratio of daily record highs to daily record lows in the lower 48 United States, from Meehl et al, "Relative increase of record high maximum temperatures compared to record low minimum temperatures in the U.S.," Geophysical Research Letters, 2009.
Mike Shibao/University Corporation for Atmospheric Research

That study only runs through 2006, however. So can we bring it up to date?

The Weather Channel's Guy Walton, a coauthor on the paper cited above, keeps a regular tally of NCDC weather records, and emails out his compilation to interested parties. One limitation is that according to Walton, this approach does not control for different weather station ages or other complicating factors. In other words, these data are not as carefully scrubbed as those used in the peer-reviewed study above. Nonetheless, based on Walton's latest analysis of the data, the decade of the 2000s saw 312,746 daily record highs, compared with only 156,494 daily record lows, for a roughly 2-1 ratio overall. And if you consider the 2010s so far, Walton's data show 91,383 daily record highs, compared with only 38,881 record lows, for a ratio that is well over 2-to-1.

So in sum: January has been a cold month for the United States. But it's not reflective of the recent past, nor of what's expected over the long term.

Advertise on MotherJones.com

Obama Just Doubled Down on His Climate Plan—Here's What Else He Could Do

| Tue Jan. 28, 2014 12:51 PM EST

Updated 1/28/14, 10:30 pm ET: Reminding lawmakers that the debate over climate science is "settled," President Obama used his State of the Union address tonight to reiterate his administration's commitment to adopting stringent new regulations on greenhouse gas emissions from coal-fired power plants and tougher fuel efficiency rules for heavy trucks.

But Obama also doubled down on his controversial "all-of-the-above" energy strategy. He touted the role that natural gas extraction has played in reducing US carbon emissions while also saying he would work with the fracking industry to adopt stronger environmental protections.

But even with an obstinate and unproductive Congress, these aren't the only policy options available to the president; last week, the Center for the New Energy Economy at Colorado State University released a report co-authored by former Colorado governor Bill Ritter that details 200 climate actions Obama could take without Congress.

Earlier today, we outlined a few ideas:

1. Continue the crackdown on coal pollution: This month the Environmental Protection Agency released a new draft of rules that would strictly curtail emissions of carbon dioxide from new coal-fired power plants; a second set of rules that would apply to existing plants is expected later this year. Slashing greenhouse gas emissions from power plants, which account for roughly a third of country's total GHG emissions, is a major pillar of the president's climate platform, even though a lengthy review process and probable legal challenges from the coal industry mean the rules aren't likely to take effect before the end of his term. But in the absence of a national price on carbon or other legislation, regulations like this are the most significant way the president can promote a transition away from our dirtiest power sources. 

2. Fix fracking: Today, regulations for natural gas drilling companies are mainly applied by states, but the president has an opportunity to influence the industry's practices when it shows up to drill on federal land. The Colorado State report calls on the Bureau of Land Management to apply stringent rules for fracking on public land, like full disclosure of what's in the fracking chemical cocktail, zero tolerance for methane leaks from wells and pipes (a major, unregulated source of highly potent greenhouse gases), and more efficienct water-use practices. The president also needs to set a more concrete timeline for how long fracking, often described as a "bridge" fuel between coal and renewables, will continue to be a major source of domestic energy, said Bill Becker, the report's co-author and executive director of the Presidential Climate Action Project.

"We recognize that natural gas is a logical transition fuel," Becker added. "But we think that should be happening a lot faster than it's happening now."

Somehow, Becker said, the president needs to reconcile his "all of the above" energy plan with his stated goals for reducing greenhouse gas emissions 17 percent below 2005 levels by 2020; working with the fracking industry to cut methane leaks is a great place to start.

Donald Trump's Climate Conspiracy Theory

| Mon Jan. 27, 2014 12:53 PM EST

When chilling cold first descended in early January, we had an occasion to correct Donald Trump on climate science. To do so, we simply explained that the widely recognized phenomenon known as winter doesn't refute global warming, especially since winter is inherently limited to one hemisphere. (In a widely lampooned tweet, Trump had cited "record low temps" in arguing that "this very expensive GLOBAL WARMING bullshit has got to stop.")

Alas, Trump has now dug himself deeper into the snow drift. Here are the latest tweets:

With this, Trump joins the grand tradition of climate science conspiracy theorizing, as epitomized by Senator James Inhofe 2012 book title: The Greatest Hoax: How the Global Warming Conspiracy Threatens Your Future. By using the word "hoax," Inhofe and Trump are suggesting that there is a conscious attempt to mislead us with fake, trumped up science, in the service of political goals.

So how do you refute this global warming conspiracy theory? Simple: You merely have to explain what a real global warming conspiracy would actually entail, whereupon the utter implausibility of the scenario becomes obvious.

For a global warming conspiracy to exist, you'd need scientists around the world to be in on it. Not scientists at one university, or scientists in one country. Scientists everywhere, from Australia to Japan, from China to America.

This is scarcely possible, especially in light of the incentive structure in science: Scientists advance and get promoted by publishing original research that is highly cited by other scientists. And it is hard to imagine a better citation-grabbing paper than one that seriously refuted what most scientists in a given field believe to be true. There is therefore a huge incentive for a scientist or group of scientists to upset everything we thought we knew about climate change, assuming that this could be achieved in a serious scientific paper that passes peer review and stands the test of time. A researcher who achieved such a feat would be on a parallel, as far as fame and renown goes, with someone like Alfred Wegner, who originally proposed the revolutionary idea of continental drift.

The incentives, therefore, are very much against maintaining a climate conspiracy. The incentives instead tilt towards exposing it. And that makes the 97-percent consensus on climate change among scientists publishing in the peer-reviewed literature that much more powerful.

Finally, let's take on this idea that scientists are in it for the money, which may or may not be implied by Trump's first tweet above, but is a frequent fixture of global warming conspiracy theories. According to 2012-2013 data from the American Association of University Professors, the average salary for a US assistant professor at a doctorate-granting institution was $76,822. Salaries rise as high as an average of $134,747 for full professors at doctorate-level institutions, but that's academia's most coveted level, and not everybody gets there.

Surely Trump and other conservatives who believe in the power of the free market can see that people who want the big bucks are likely to embark on a different career path.

No, Climate Change Is Not Waking Bears From Hibernation

| Thu Jan. 23, 2014 2:33 PM EST
A black bear hunkers down near a pile of garbage in Sacramento last fall.

Last week, a rogue black bear made a cameo appearance for skiers at the Heavenly Mountain Resort near Lake Tahoe. The month before, a 260-pound male bear had to be put down by wildlife officials after breaking into several cars and a home in the same area. The spate of run-ins comes as California's brutal drought lingers on, with snowpack in the Sierra Nevada at a fifth of its normal level, leading several news outlets to suggest that balmy conditions have led bears here to awaken prematurely from their annual winter slumber.

That's a nice hypothesis, but according to the California Department Fish and Wildlife, there's nothing to it. Five to 15 percent of the Tahoe area's 300 black bears stay awake every winter, said CDFW biologist Jason Holley, and "we don't have any evidence to support that there's any more this winter." In fact, Holley said, the last few months of 2013 saw fewer bear complaints than average.

SF Chron front page
The front page of a recent San Francisco Chronicle. There's no evidence that more bears are awake this year than in an average year, officials said. Clara Jeffery/Mother Jones

So why all the hullabaloo? Holley's guess is that the drought cut down supplies of the bears' natural food sources—mainly grass, berries, and insects, although they'll eat just about anything—forcing those that are normally awake anyway to wander further afield, i.e., onto your ski slope or into your backyard. Not that the bears mind much.

"They are very adaptive and very mobile, so they will usually be able to take care of their daily needs in a drought situation," Holley said. "But then they're coming down to the lake to drink a lot, coming down for food. If the drought persists, it greatly increases the odds of a negative interaction with people."

What motivates some bears to stay awake while others hibernate is still somewhat of a mystery to scientists, according to Roger Baldwin, a wildlife specialist at the University of California-Davis who has conducted extensive research on bear behavior. When small mammals (a squirrel, say) hibernate, their heart rate and body temperature drop radically, toeing death's doorstep without actually stepping over, and stay that way for several months. Black bears, on the other hand, are much less extreme: They crank down their metabolism, heart rate, and body temperature just enough to get seriously lazy, but are still with it enough to be "perfectly capable of taking a swipe at you if you crawl into the den with them," Baldwin said, so rousting them is neither uncommon nor difficult.

These 11 Popular Sodas Tested Positive for a Potential Carcinogen

| Thu Jan. 23, 2014 7:05 AM EST

The chemical compound that gives some sodas a caramel-brown color could be a carcinogen—and according to a new study by Consumer Reports, it's in many popular soft drinks at levels that exceed what many experts consider safe. Between April and December of 2013, researchers tested 110 bottles of various brands of soda for the 4-methylimidazole, or 4-MeI for short. They found the highest levels of the substance in Goya Malta, a malt-flavored soda popular in Latin American communities, and in various Pepsi products:

Consumer Reports Chart
Click for a larger version. Courtesy of Consumer Reports

4-MeI is not federally regulated, but the International Agency for Research on Cancer lists it as a potential carcinogen (PDF). In California, products that expose consumers to more than 29 micrograms of 4-MeI are supposed to have a warning label, according to the state's Proposition 65—yet none of the sodas that the group tested carried such a label. Dr. Urvashi Rangan, a toxicologist and executive director of the Consumer Reports Food Safety and Sustainability Center, believes that one reason for the New York samples' relatively high levels of 4-MeI might be that New York doesn't have a similar warning-label rule.

The researchers found that the Coca-Cola products had relatively low levels of 4-MeI. On the other hand, some of the samples of Dr. Snap, a soda sold at Whole Foods with a "natural" label, had levels that exceeded the California warning-label threshold.

PepsiCo representatives told Consumer Reports that they don't attach the warning label to their products in California because their research shows that consumers drink only about a third of a can of their products a day, on average—an amount that contains less than 29 micrograms of 4-MeI. The other brands whose products Consumer Reports tested have not yet responded to the findings.

Rangan notes that 4-MeI is present in some foods as well: barbecue sauces, soups, imitation pancake syrup, gravy, and canned mushrooms, among others. While Consumer Reports is urging the FDA to regulate 4-MeI, in the meantime, consumers should consider avoiding foods and beverages with caramel color, Rangan says. "We just don't think coloring your food brown should give you cancer."

NASA: 2013 Tied for the 7th-Hottest Year on Record

| Wed Jan. 22, 2014 10:55 AM EST
Your anomalously hot planet in 2013.

Yesterday, NASA and the National Oceanographic and Atmospheric Administration jointly put the year 2013 in its climate context. It was a very hot one: NASA's data have 2013 in a three-way tie for the seventh-hottest year in recorded history, while NOAA's have it in a three-way tie for the fourth hottest. (The gap arises due to slight differences in how the two agencies take into account matters like the warming of the Arctic, where there are relatively few weather stations.)

But those little discrepancies don't matter that much, explains NASA's Gavin Schmidt, who is deputy chief of the agency's Goddard Institute for Space Studies. What really matters is the larger pattern, and here there's really no disagreement. "The fact of the matter is that the long-term trends are very clear," says Schmidt.

How clear? NOAA and NASA agree that with the exception of 1998 (the year of a record-breaking El Nino event), every single one of the top 10 hottest years has occurred since the year 2000. They have slight differences in their rankings, to be sure, but on that big-picture question, there really isn't any daylight between the two agencies.

Similarly, their assessments of long-term global warming show a remarkable similarity:

Global warming. NASA/NOAA

But hasn't global warming "slowed down"? Schmidt agrees that the rate of warming over the 2000s wasn't quite as rapid as during the 1990s, something scientists are still working on understanding a bit better. But at the same time, the new analysis shows that the 2000s were considerably warmer than any previous decade. And Schmidt expects the 2010s to be hotter than the 2000s, and so on. And so on.

"If you look decade by decade, it's clear that the last decade is warmer than the decade before, which is warmer than the decade before," says Schmidt. "And we don't anticipate that changing."

Advertise on MotherJones.com

Believe It: Global Warming Can Produce More Intense Snows

| Tue Jan. 21, 2014 2:44 PM EST
Satellite image of the intense US blizzard of February 5-6, 2010.

We all remember "Snowmageddon" in February of 2010. Even as Washington, D.C., saw 32 inches of snowfall for the month of February—more than it has seen in any February since 1899—conservatives decided to use the weather to mock global warming. Oklahoma Senator James Inhofe and his family even built an igloo on Capitol Hill and called it "Al Gore's New Home." Har har.

Yet at the same time, scientific voices were pointing out something seemingly counterintuitive, but in fact fairly simple to understand: Even as it raises temperatures on average, global warming may also lead to more intense individual snow events. It's a lesson to keep in mind as the northeast braces for winter storm Janus—which is expected to deliver as much as a foot of snow in some regions—and we can expect conservatives to once again mock climate change.

To understand the relationship between climate change and intense snowfall, you first need to understand that global warming certainly doesn't do away with winter or the seasons. So it'll still be plenty cold enough for snow much of the time. Meanwhile, global warming loads the dice in favor of more intense precipitation through changes in atmospheric moisture content. "Warming things up means the atmosphere can and does hold more moisture," explains Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo. "So in winter, when there is still plenty of cold air there's a risk of bigger snows. With east coast storms, where the moisture comes from the ocean which is now warmer, this also applies."

Why does the atmosphere hold more moisture? The answer is a key physical principle called the Clausius-Clapeyron equation, stating that as atmospheric temperature rises, there is an exponential increase in the amount of water vapor that the air can hold—leading to more potential precipitation of all types. (A detailed scientific explanation can be found here.)

Indeed, scientific reports have often noted the snow-climate relationship. An expansive 2006 study of US snowstorms during the entirety of the 20th century, for instance, found that they were more common in wetter and warmer years. "A future with wetter and warmer winters...will bring more snowstorms than in 1901-2000," the paper predicted. There is also a clear increase in precipitation in the most intense precipitation events, especially in the northeast:

Percent increases in the amount of precipitation occurring in the heaviest precipitation events from 1958 to 2007. US Global Change Research Program.

"More winter and spring precipitation is projected for the northern U.S., and less for the Southwest, over this century," adds the draft US National Climate Assessment. Precipitation of all kinds is expected to increase, the study notes, but there will be large regional variations in how this is felt.

"The old adage, 'it's too cold to snow,' has some truth to it," observes meteorologist Jeff Masters, co-founder of the Weather Underground. "The heaviest snows tend to occur when the air temperature is near the freezing mark, since the amount of water vapor in the air increases as the temperature increases. If the climate in a region where it is 'too cold to snow' warms to a level where more snowstorms occur near the freezing point, an increase in the number of heavy snowstorms is possible for that region."

In fairness, global warming is also expected to decrease overall snow cover, because intense snow events notwithstanding, snow won't last on the ground as long in a warmer world. In fact, a decrease in snow cover is already happening.

Today's snows will usher in a new northeast cold spell, not as intense as the "polar vortex" onslaught of two weeks ago but still pretty severe. But a temporary burst of cold temperatures doesn't refute climate change any more than a major snowstorm does. Indeed, we have reasons to expect that the rapid warming of the Arctic may be producing more cold weather in the mid-latitudes in the Northern hemisphere. For an explanation of why, listen to our interview with meteorologist Eric Holthaus on a recent installment of Inquiring Minds (from minutes 2 through 12 below):

None of this is to say, of course, that global warming explains single events; its effect is present in overall changes in moisture content, and perhaps, in the large-scale atmospheric patterns that bring us our weather.

Still, that's more than enough to refute conservatives who engage in snow trolling.

6 Scary Facts About California's Drought

| Sat Jan. 18, 2014 7:00 AM EST
Satellite views of the Sierra Nevada, a year apart.

"Fire season just didn't end this year."

The comment came from Scott Miller, the Los Angeles County fire inspector, in the wake of the Colby Fire in the foothills near Los Angeles. The fire is now 30-percent contained, but it serves as the latest reminder that California is facing an increasingly alarming drought—one that yesterday prompted Gov. Edmund Brown, Jr., to declare a state of emergency.

Last year was California's driest on record for much of the state, and this year, conditions are only worsening. Sixty-three percent of the state is in extreme drought, and Sierra Nevada snowpack is now running at just 10 to 30 percent of normal. "We're heading into what is near the lowest three year period in the instrumental record" for snowpack, says hydrologist Roger Bales of the University of California-Merced.

Water shortages, devastating wildfires, and growing economic impacts: All could be on the way unless more precipitation arrives, and fast. Here are some scary realities about the drought:

1. It's Bordering on Unprecedented in Some Areas. According to Christopher Burt, weather historian at Weather Underground, the City of San Francisco has received only 2.12 inches of water so far in this water year. The driest water year on record was from 1850-1851, at 7.42 inches. So as of now, San Francisco is below half of the all-time record low.

2. Time in the Rainy Season is Running Out. California doesn't get steady rain all year round. Rather, it has a rainy season each year, and we're currently in it. Typically, the rainy season runs through March; if major precipitation doesn't arrive by then, it probably won't be coming. Granted, this is also the chief source of hope right now: California can sometimes get plenty of water in February and March.

3. The Drought Could Lead to Dirtier Energy Use. Peter Gleick, president of the Oakland-based Pacific Institute, points out one less-noticed consequence of the drought: The lack of water means less available hydropower. And that has consequences: "Because renewable hydropower is among the cheapest and most versatile of electricity sources," writes Gleick, "California ratepayers will have to pay for more costly fossil fuels to make up for the difference." The result, he notes, is likely to be "billions of dollars in added energy costs and generating more greenhouse gases to the atmosphere."

4. It's Setting the Stage for a Devastating Fire Season. Hotter, drier conditions favor wildfires. Indeed, California has already seen several significant fires since the October 31 end of the traditional fire season, including December's Big Sur fire and the ongoing Colby Fire in the Los Angeles area. That's a bad sign. So is the fact that in just the first 11 days of January, the state saw 154 fires that burned 598 acres. That's way above the five-year average for this time of year.

For California, seven of the 10 largest fires in state history have occurred since the year 2000. And if these dry conditions persist throughout 2014, another new fire may be added to that list.

5. It Could Pummel Agriculture. California is an agricultural powerhouse. For crops, the state accounts for 15 percent of national sales and for livestock, 7.1 percent, according to the California Department of Food and Agriculture. But now farmers are likely to have considerably less water. This won't lead to agricultural collapse, but it will definitely take a toll. "There will be, in agriculture, fewer plantings, fewer harvests, and revenue of seasonal crops," says UC-Merced's Roger Bales. "There could be more expensive pumping of groundwater. And there could be just lower yields if they have less water to apply."

6. It's a Sign of What's to Come. NOAA's seasonal drought outlook projects persistent or worsening conditions in California through April:

US seasonal drought outlook. National Weather Service

Over the longer term, climate projections suggest that this risk will continue or increase. According to the draft National Climate Assessment, the US Southwest—which includes California and five other states—can expect less precipitation, hotter temperatures, and drier soils in the future, meaning that by 2060, there could be as much as a 35-percent increase in water demand. Along with that comes a 25- to 50-percent increased risk of water shortages.

So even if California gets some much needed rain in the coming months, that'll only be a short-term reprieve. Right now, the state needs to engage in some major climate adaptation planning, to get ready for a much drier future.

PHOTOS: Koalas, Tennis Players Grapple with Australian Heat Wave

| Fri Jan. 17, 2014 6:50 PM EST

Parts of Australia are in the midst of a massive heat wave, straining resources and sparking fires. Matches had to be suspended at the Australian Open in Melbourne, where temperatures hit 109 degrees Fahrenheit. Here are photos showing the toll this extreme heat has taken on the country's forests, animals, and visiting tennis stars.

Victoria brushfire
A fire-fighting helicopter extinguishes a fire burning throughout Victoria's Grampians region. Country Fire Authority/ZUMA

 

 

Australian Open fountain
Fans cool off in a fountain outside the Rod Laver Arena on day five of the Australian Open. Jason O'Brien/ZUMA

 

 

Serena Williams
Despite the heat, Serena Williams set a tournament record by winning her 61st Australian Open match. Ken Hawkins/ZUMA

 

 

Global-Warming Denial Hits a 6-Year High

| Fri Jan. 17, 2014 7:00 AM EST
Fox News on the morning of September 27, 2013, covering the new IPPC report on climate change.

The latest data is out on the prevalence of global warming denial among the US public. And it isn't pretty.

The new study, from the Yale and George Mason University research teams on climate change communication, shows a 7-percentage-point increase in the proportion of Americans who say they do not believe that global warming is happening. And that's just since the spring of 2013. The number is now 23 percent; back at the start of last year, it was 16 percent:

The percentage of Americans who believe global warming is human-caused has also declined, and now stands at 47 percent, a decrease of 7 percent since 2012.

At the same time, the survey also shows an apparent hardening of attitudes. Back in September 2012, only 43 percent of those who believed that global warming isn't happening said they were either "very sure" or "extremely sure" about their views. By November of last year, that number had increased to 56 percent.

Overall, more Americans now say they have all the information they need to make up their minds about the climate issue, and fewer say they could easily change their minds:

Increasing righteousness about global warming, on both sides of the issue Yale and George Mason teams on Climate Change Communication.

The obvious question is, what happened over the last year to produce more climate denial?

According to both Anthony Leiserowitz of Yale and Ed Maibach of George Mason, the leaders of the two research teams, the answer may well lie in the so-called global warming "pause"—the misleading idea that global warming has slowed down or stopped over the the past 15 years or so. This claim was used by climate skeptics, to great effect, in their quest to undermine the release of the UN Intergovernmental Panel on Climate Change's Fifth Assessment Report in September 2013—precisely during the time period that is in question in the latest study.

As we have reported before, the notion of a global warming "pause" is, at best, the result of statistical cherry-picking. It relies on starting with a very hot year (1998) and then examining a relatively short time period (say, 15 years), to suggest that global warming has slowed down or stopped during this particular stretch of time. But put these numbers back into a broader context and the overall warming trend remains clear. Moreover, following the IPCC report, new research emerged suggesting that the semblance of a "pause" may be the result of incomplete temperature data due to the lack of adequate weather stations in the Arctic, where the most dramatic global warming is occurring.

Nonetheless, widely publicized "pause" claims may well have shaped public opinion. "Beginning in September, and lasting several months, coincident with the release of the IPCC report, there was considerable media attention to the concept of the 'global warming pause,'" observes Maibach. "It is possible that this simple—albeit erroneous—idea helped to convince many people who were previously undecided to conclude that the climate really isn't changing."

"Even more likely, however," Maibach adds, "is that media coverage of the 'pause' reinforced the beliefs of people who had previously concluded that global warming is not happening, making them more certain of their beliefs."

As Maibach's colleague Anthony Leiserowitz of Yale adds, it isn't as though those who were already convinced about global warming became less sure of themselves over the last year. Rather, the change of views "really seems to be happening among the 'don't knows,'" says Leiserowitz. "Those are the people who aren't paying attention, and don't know much about the issue. So they're the most open-minded, and the most swayable based on recent events."

Journalists take heed: Your coverage has consequences. All those media outlets who trumpeted the global warming "pause" may now be partly responsible for a documented decrease in Americans' scientific understanding.