Despite the scientific consensus that human-caused global warming is real and is negatively affecting our planet, those who disagree continue to receive a significant amount of attention from the media. A recent example was the March 29 New York Times Magazine cover story about physicist Freeman Dyson, who argues that global warming is not a significant problem. More broadly, throughout the past year, the media have repeatedly provided a platform for critics who argue that the globe is in a period of “cooling,” while often failing to challenge their suggestion that this shows that global warming is a myth. These critics often misleadingly cite the fact that the average global temperature in 2007 and 2008 was cooler than it was in 1998, echoing an April 4, 2008, BBC article, which reported that “temperatures have not risen globally since 1998 when El Nino warmed the world.” Other times, the claim is made by media figures themselves; for instance, syndicated columnist George Will wrote in his widely criticized February 15 Washington Post column that “according to the U.N. World Meteorological Organization [WMO], there has been no recorded global warming for more than a decade” -- despite repeated statements by the WMO and its representatives the Earth remains in a warming trend.

In fact, climate experts reject the idea that the relatively cooler global average temperatures in several of the last 10 years are any indication that global warming is slowing or does not exist. Scientists have identified a long-term warming trend spanning several decades that is independent from the normal climate variability -- which includes relatively short-term changes in climate due to events like El Niño and La Niña -- to which they attribute the recent cooler temperatures.

In a February 11 Guardian op-ed, Vicky Pope, the head of climate change advice at the U.K. Met Office Hadley Centre, explained that claims about the pace of global warming require more than 10 years of data, “since natural variations always occur on this timescale.” She continued, “1998 was a record-breaking warm year as long-term man-made warming combined with a naturally occurring strong El Niño. In contrast, 2008 was slightly cooler than previous years partly because of a La Niña. Despite this, it was still the 10th warmest on record.”

According to the Met Office website, the WMO “requires the calculation of averages for consecutive periods of 30 years,” which was chosen “as a period long enough to eliminate year-to-year variations.”

In a letter to the editor of The Washington Post published on March 21, WMO secretary-general Michel Jarraud responded to Will's column, writing that "[i]t is a misinterpretation of the data and of scientific knowledge to point to one year as the warmest on record ... and then to extrapolate that cooler subsequent years invalidate the reality of global warming and its effects." Jarraud wrote:

Data collected over the past 150 years by the 188 members of the World Meteorological Organization (WMO) through observing networks of tens of thousands of stations on land, at sea, in the air and from constellations of weather and climate satellites lead to an unequivocal conclusion: The observed increase in global surface temperatures is a manifestation of global warming. Warming has accelerated particularly in the past 20 years.

It is a misinterpretation of the data and of scientific knowledge to point to one year as the warmest on record -- as was done in a recent Post column [“Dark Green Doomsayers,” George F. Will, op-ed, Feb. 15] -- and then to extrapolate that cooler subsequent years invalidate the reality of global warming and its effects.

The difference between climate variability and climate change is critical, not just for scientists or those engaging in policy debates about warming. Just as one cold snap does not change the global warming trend, one heat wave does not reinforce it. Since the beginning of the 20th century, the global average surface temperature has risen 1.33 degrees Fahrenheit.

Evidence of global warming has been documented in widespread decreases in snow cover, sea ice and glaciers. The 11 warmest years on record occurred in the past 13 years.

While variations occur throughout the temperature record, shorter-term variations do not contradict the overwhelming long-term increase in global surface temperatures since 1850, when reliable meteorological recordkeeping began. Year to year, we may observe in some parts of the world colder or warmer episodes than in other parts, leading to record low or high temperatures. This regional climate variability does not disprove long-term climate change. While 2008 was slightly cooler than 2007, partially due to a La Niña event, it was nonetheless the 10th-warmest year on record.

The Intergovernmental Panel on Climate Change, co-sponsored by the WMO, has confirmed through observations and increasingly sophisticated and realistic models that regional variability has increased and will continue to increase as global surface temperatures rise. This is likely to result in more weather and climate extremes, such as droughts, floods, storms and heat waves. Responding to these challenges will require the collaborative efforts of all countries and of scientists in multiple disciplines to develop adaptation strategies to reduce the risk of disaster. This topic is scheduled for discussion at the World Climate Conference-3 beginning Aug. 31 in Geneva.

Further, the April 2008 BBC article that reported that “temperatures have not risen globally since 1998 when El Nino warmed the world” also reported that Jarraud disputed the notion that “this means global warming has peaked.”

From the revised version of the BBC article:

Global temperatures for 2008 will be slightly cooler than last year as a result of the cold La Nina current in the Pacific, UN meteorologists have said.

The World Meteorological Organization's secretary-general, Michel Jarraud, told the BBC it was likely that La Nina would continue into the summer.

But this year's temperatures would still be way above the average -- and we would soon exceed the record year of 1998 because of global warming induced by greenhouse gases.

The WMO points out that the decade from 1998 to 2007 was the warmest on record. Since the beginning of the 20th Century, the global average surface temperature has risen by 0.74C.

[...]

“When you look at climate change you should not look at any particular year,” he said. “You should look at trends over a pretty long period and the trend of temperature globally is still very much indicative of warming.

”La Nina is part of what we call 'variability'. There has always been and there will always be cooler and warmer years, but what is important for climate change is that the trend is up; the climate on average is warming even if there is a temporary cooling because of La Nina."

Similarly, in a January 11, 2008, post on RealClimate.org, Gavin Schmidt, a climate modeler at the NASA Goddard Institute for Space Studies, wrote that “short term comparisons” of weather and climate are “misguided.” According to Schmidt, “the climate system has enormous amounts of variability on day-to-day, month-to-month, year-to-year and decade-to-decade periods. Much of this variability (once you account for the diurnal cycle and the seasons) is apparently chaotic and unrelated to any external factor -- it is the weather”:

Some aspects of weather are predictable -- the location of mid-latitude storms a few days in advance, the progression of an El Niño event a few months in advance etc, but predictability quickly evaporates due to the extreme sensitivity of the weather to the unavoidable uncertainty in the initial conditions. So for most intents and purposes, the weather component can be thought of as random.

If you are interested in the forced component of the climate -- and many people are -- then you need to assess the size of an expected forced signal relative to the unforced weather 'noise'. Without this, the significance of any observed change is impossible to determine. The signal to noise ratio is actually very sensitive to exactly what climate record (or 'metric') you are looking at, and so whether a signal can be clearly seen will vary enormously across different aspects of the climate.

Schmidt wrote that “if you start to take longer trends, then the uncertainty in the trend estimate approaches the uncertainty in the expected trend, at which point it becomes meaningful to compare them since the 'weather' component has been averaged out. In the global surface temperature record, that happens for trends longer than about 15 years, but for smaller areas with higher noise levels (like Antarctica), the time period can be many decades.”

Nonetheless, media figures have, on numerous occasions, advanced this falsehood or allowed it to go unchallenged:

• On the March 26, 2009, edition of CNBC's The Kudlow Report, anchor Larry Kudlow asserted that “global warming ... is now being disputed for global cooling.”

• On the March 2, 2009, edition of his Fox News program, Sean Hannity, while referring to “environmental nut cases,” said, “Every time they have a global warming summit or -- it snows.” Former McCain presidential campaign adviser Nancy Pfotenhauer replied in part: "[I]t's hilarious, 'cause when you talk to the scientists, they said, 'you could make the case just as much for global cooling,' and then, you know, that they're -- that this stuff has just run amuck."

• Appearing on the March 2, 2009, edition of Fox News' Special Report, senior political analyst Brit Hume said the Earth “has seen no average warming for the past 10 years.” Hume acknowledged that "[t]here does seem to have been some increase in the average Earth temperature during the last part of the 20th century" and that “there are computer models that say this trend will continue with profound effects on the way we live.” But he then asserted that "[t]he problem with these models is that when data from the past have been plugged into them, they have had trouble predicting today's temperatures. The climate alarmists certainly did not foresee the cooling trend of the past decade."

• On the February 2, 2009, edition of MSNBC's 1600 Pennsylvania Avenue, syndicated columnist Deroy Murdock touted climate change skeptic Martin Hertzberg's assertion that global warming is not occurring because, in Murdock's words, “the Earth temperature has gone down 1.8 degrees Fahrenheit since 1997.” Murdock was referencing the following quote from Hertzberg that Murdock included in a February 1 column: "[T]he average temperature of Earth's atmosphere has declined over the last 10 years. From the El Nino Year of 1998 until Jan. 2007, it dropped a quarter of a degree Celsius (0.45 degrees Fahrenheit). From Jan 2007 to the spring of 2008, it dropped a whopping three-quarters of a degree Celsius (1.35 degrees Fahrenheit)."

• On the January 6, 2009, edition of CNN Newsroom, anchor Heidi Collins said, “New research is heating up the global warming issue once again. The data suggests a split on whether the planet is truly in peril.” Then, in a report, CNN correspondent Ines Ferré said, “A confusing picture of our world's climate: Three independent research groups found that 2008 was the ninth or 10th warmest year since 1850 when record-keeping began, but it also was the coolest year since the turn of the 21st century.” Ferré then aired a clip of Weather Channel co-founder Joseph D'Aleo saying “We are too short-sighted or certainly the -- those who believe in it are not looking at all the big picture, which needs to include other factors than natural cycles in the ocean and of the sun that are the real drivers.”

• On the January 5, 2009, edition of Special Report, anchor Bret Baier said: “Despite dire warnings from global warming alarmists ... former nuclear scientist and energy expert Michael Fox writes in the Hawaii Reporter that 2008 was, quote, 'another grim year for the global warmers. ... 2008 marked the tenth consecutive year of no global warming. ... The Earth has been cooling for the last six years.' ”

• Lou Dobbs said during the introduction of his December 18, 2008, CNN show: “And tonight, unusual winter storms are dumping snow in unusual places across Western states, and a huge snowstorm is headed toward the Northeast. This is global warming?” During his segment on the issue, Dobbs hosted Heartland Institute senior fellow and science director Jay Lehr, who at one point during the interview said: “We've been warming out of that cold spell from the Revolutionary War period, and now we're back into a cooling cycle. The last 10 years have been quite cool. And right now I think we're going in to cooling rather than warming, and that should be a much greater concern for humankind. But all we can do is adapt. It is the sun that does it, not man.”

• In a November 25, 2008, Politico article, Erika Lovley wrote that "[c]limate change skeptics on Capitol Hill are quietly watching a growing accumulation of global cooling science and other findings that could signal that the science behind global warming may still be too shaky to warrant cap-and-trade legislation." As evidence, Lovley quoted D'Aleo saying, “Recent warming has stopped since 1998, and we want to stop draconian measures that will hurt already spiraling downward economics.”

• In a June 17, 2008, column, former Washington Times editor-in-chief Wesley Pruden falsely claimed that “the earth has been measurably cooling for the last decade, despite everything [former Vice President] Al [Gore] and his followers have done about it.”

• On the August 21, 2008, edition of Special Report, Baier said, “Finally, the World Meteorological Organization says the first half of 2008 was the coolest in at least five years. It expects 2008 will almost certainly be cooler than recent years, although temperatures remain above the historical average.” He continued: “The United Kingdom Meteorological Office Hadley Centre for Climate Studies says data shows worldwide temperatures have declined since 1998. A scientist with WMO says, quote, 'We can expect with high probability this year will be cooler than the previous five years.' Climate scientists differ about whether the cooling temperatures undermine the case for man-made global warming.”

• On the April 4, 2008, edition of Fox News' America's Pulse, host E.D. Hill falsely claimed, in a teaser for an upcoming segment, that “the U.N. [United Nations] says the planet may actually cool off for the 10th year in a row.” Later, during a discussion of the issue with Greg Gutfeld, host of Fox News' Red Eye with Greg Gutfeld, Hill similarly stated: “U.N. meteorologists now saying that we could have, for the 10th year in a row, a colder year, temperatures ... decreasing, not warming, getting colder.”

By contrast, during an interview with Christopher Field, the director of the Carnegie Institution's Department of Global Ecology, on the February 17 edition of CNN's American Morning, co-host John Roberts said that “some people have been pointing this -- to this in recent days, a graph from NASA tracks temperature data from 1880 until this year. And in 1999, there was a real spike. There was also one that looks like it was about 2005 or so. But the overall trend from 1998 on has been down, and some people are suggesting that the world is actually cooling as opposed to getting warmer. What do you say about these data from NASA?” Field replied: “It's important to remember that the world's climate system is incredibly complex with a whole bunch of internal dynamics. The internal dynamics are such that, for several years at a time, you can see the average temperature go in a direction that's different from the long-term trend. The fact of the matter is that all of the recent years have been among the very hottest on record, and there is abundant evidence that, over the long run, the planet is continuing to warm, and it's highly likely that this is a consequence of the greenhouse gases that are being released by human activity.”

From the March 2 edition of Fox News' Hannity:

HANNITY: Number two: Every time they have a global warming summit or -- it snows.

PFOTENHAUER: It snows. Right.

HANNITY: You like that, coach? It cracks me up.

LOU HOLTZ (former football coach): I knew where you were going. I'll tell you what. Hey, I'm just walking over here; I don't have a coat. I'm freezing, there's eight inches of snow, and I said, thank God for global warming. I'd have really been cold.

HANNITY: Now it's the new ice age. Yeah, exactly.

PFOTENHAUER: You're right. You're exactly right.

HOLTZ: Wow. Am I lucky?

PFOTENHAUER: Well, you know, it's hilarious, 'cause when you talk to the scientists, they said, “you could make the case just as much for global cooling,” and then, you know, that they're -- that this stuff has just run amuck. But I'll tell you what: With Carol Browner in that White House, buckle up.

HANNITY: And Doug, by the way, [House Speaker] Nancy Pelosi [D-CA] couldn't make it 'cause of the snow.

From the 9 a.m. ET hour of the January 6 edition of CNN Newsroom:

COLLINS: New research is heating up the global warming issue once again. The data suggests a split on whether the planet is truly in peril. Our Ines Ferré has a story from New York.

[begin video clip]

FERRÉ: A confusing picture of our world's climate: Three independent research groups found that 2008 was the ninth or 10th warmest year since 1850 when record-keeping began, but it also was the coolest year since the turn of the 21st century.

New data from the University of Illinois says ice levels are roughly the same as those seen 29 years ago. But after decades of ice melt in the Arctic, that may be of little comfort. The increase is because of the formation of thin ice, which melts easily once the winter is over.

Even so, one climatologist, skeptical of global warming, feels the entire debate is muddled with selective data.

D'ALEO: We are too short-sighted or certainly the -- those who believe in it are not looking at all the big picture, which needs to include other factors than natural cycles in the ocean and of the sun that are the real drivers.

FERRÉ: NASA scientists report that more than 2 trillion tons of land ice in Greenland, the Arctic, and Antarctic have melted since 2003.

Some farmers fear future regulations on greenhouse gas emissions could include what it could amount to a cow tax. The United Nations calculates livestock are responsible for 18 percent of greenhouse gas emissions worldwide.

PAT MICHAELS (Cato Institute senior fellow): Extremism in the pursuit of climate policy is certainly no virtue. And what's really going on is we have rather a moderate increase in temperature, so why would one jump off the bridge and take money away from people?

From the January 5 edition of Fox News' Special Report with Bret Baier:

BAIER: Despite dire warnings from global warming alarmists, DailyTech online reports global sea ice levels are now equivalent to those seen 29 years ago.

Satellite data from the University of Illinois' Arctic Climate Research Center indicates the rate of global sea ice increase in the last four months of the year was the fastest rate of change on record.

Meanwhile, former nuclear scientist and energy expert Michael Fox writes in the Hawaii Reporter that 2008 was, quote, “another grim year for the global warmers. ... 2008 marked the tenth consecutive year of no global warming. ... The Earth has been cooling for the last six years.”

From the August 21, 2008, edition of Fox News' Special Report with Brit Hume:

BAIER: Finally, the World Meteorological Organization says the first half of 2008 was the coolest in at least five years. It expects 2008 will almost certainly be cooler than recent years, although temperatures remain above the historical average.

The United Kingdom Meteorological Office Hadley Centre for Climate Studies says data shows worldwide temperatures have declined since 1998. A scientist with WMO says, quote, “We can expect with high probability this year will be cooler than the previous five years.”

Climate scientists differ about whether the cooling temperatures undermine the case for man-made global warming.

From the February 17 edition of CNN's American Morning:

ROBERTS: All right. So, scientists and environmentalist talk about a threshold, the certain number of parts per million in greenhouse gases beyond -- which they call a tipping point -- beyond which it may be impossible to reverse global warming. This new data that you have been talking about -- these new data -- does that change that tipping point? Does it accelerate it? Might we already be there, as some scientists are suggesting?

FIELD: One of the critical important goals for climate research is to figure out where these tipping points are. The fact of the matter is that we can't be 100 percent confident. There is abundant evidence that these threshold conditions are out there somewhere. It's an active area of research. And I think what we're calling for is caution about approaching them too quickly, given that we don't know exactly where they are.

ROBERTS: You know, I'm holding in my hand, and some people have been pointing this -- to this in recent days, a graph from NASA tracks temperature data from 1880 until this year. And in 1999, there was a real spike. There was also one that looks like it was about 2005 or so. But the overall trend from 1998 on has been down, and some people are suggesting that the world is actually cooling as opposed to getting warmer. What do you say about these data from NASA?

FIELD: It's important to remember that the world's climate system is incredibly complex with a whole bunch of internal dynamics. The internal dynamics are such that, for several years at a time, you can see the average temperature go in a direction that's different from the long-term trend.

The fact of the matter is that all of the recent years have been among the very hottest on record, and there is abundant evidence that, over the long run, the planet is continuing to warm, and it's highly likely that this is a consequence of the greenhouse gases that are being released by human activity.