One of the most familiar memes we hear from the climate-change deniers is the phrase, “Global warming ended in 1998 and it’s been cooling since then.” You find something along these lines on most of the AGW denier books and websites, and it is repeated endlessly as if somehow repetition makes it more true. This is just like creationists who continually repeat the phony argument that “evolution violates the Second Law of Thermodynamics”, even though this is patently false. As has been pointed out many times, the Second Law only applies to closed systems. The earth is not a closed system since it receives energy from the sun. Yet in every creationist book and website and debate for many decades now you’ll hear them repeat it over and over again, since it sounds impressive to their scientifically unsophisticated audience and apparently they cannot understand why it’s wrong, or they don’t care as long as it suits their political agenda.
One of the most famous examples of the “cooling since 1998″ meme occurred when conservative pundit George Will wrote in a Feb. 15, 2009 Washington Post column, “Dark Green Doomsayers,” that “According to the World Meteorological Organization,there has been no record of global warming for more than a decade.” The same column also printed false claims about the retreat of the glaciers, and about scientists predicting global cooling back in the 1970s (all discussed and debunked in Jim Powell’s new book The Inquisition of Climate Science, pp. 75-79). Will was taken to task by climate scientists all around the world for his mistakes and misrepresentations, but he never retracted them. The Washington Post ombudsman tried to justify running Will’s column and rationalize their lax fact-checking procedure, writing that “opinion columnists are free to choose whatever facts bolster their arguments. But they are not free to distort them.” Eventually, the uproar was so great at Will’s egregious distortions that the Post printed two separate columns rebutting him. Apparently learning nothing from the experience, Will dug an even deeper hole by again claiming in an April 2, 2009, column that there hasn’t been a warmer year since 1998.
The problem with Will’s statement—and all those made by AGW deniers who repeat the meme—is that it is false! Picking 1998 as a starting point is a classic example of cherry-picking data to show what you want it to show, and a deliberate attempt to distort the actual record. As climatologists have known for years, 1998 was an exceptionally warm year due to a record El Niño, which boosted average global temperature way above the overall trend from the past few decades. During El Niño years, the marine circulation patterns release a lot of tropical heat from the oceans and raise overall global temperature for a short time. Likewise, 2008 was a La Niña year, and it was cooler than normal. These are part of the year-to-year “noise” in the system of global temperatures that is well known to scientists. Scientists nevertake a single year’s temperature and then connect it to another data point and claim it’s a “trend.” Instead, the only rigorous and scientifically defensible method is to look at the long-term trends in climate over decades and “smooth” the curve using rolling averages, so that a more statistically meaningful curve fit can be performed.
Such a procedure is performed in the plot shown here, where the curve fit filters out the noise and shows the overall trend in the data—and by any objective measure, global temperatures are clearly increasing dramatically over the past century. This is the same answer that all the other climate indicators have been giving for years, and this is part of the reason why over 95-99% of climate scientists agree that AGW is real.
In response to Will’s column, Michael Jarraud, the secretary-general of the World Meteorological Organization (whose data Will misused) wrote:
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….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 global 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 [this was written in 2009].
If this is the reality, what about Will’s claim that climate has cooled since 1998? You can squint at the last few data points on the curve and see the 1998 El Niño spike clearly—but it is also clear that it is just a one-year spike, and not representative of the trend over 5 years or 10 years or longer. The message of the curve is clear: global temperatures are warming dramatically, and the El Niño event of 1998 is just a wiggle in the overall trend. To report the story any other way is a clear distortion of the data.
Making the point clearer, I’ve replotted the last 20 years of NASA-GISS data on a more expanded graph, so we can focus on the details, and I’ve also updated the data through 2010 (we should have the data for 2011 soon, but already the winter of 2011-2012 is the fourth warmest on record; the previous 3 hottest were all in the past 20 years). As you can see from the plot, the warming trend since 1989 shows up clearly, as does the anomalous spike in 1998. Yet the AGW denier cherry-pickers start with the anomalously warm 1998 data then try to make the case that the next few years are cooler, hence, “no global warming”. However, this falls apart in 2002 and 2003, which were as warm as 1998 (without El Niño events), and 2005, 2006, 2007, 2009, and 2010 were as warm as 1998 or even warmer still. As the quote above pointed out, as of 2009, 11 of the warmest years on record had occurred in since 1986, and adding 2009 and 2010, that makes 13 of the warmest years on record in the past 15 years. All of the sixteen hottest years ever recorded on a global scale have occurred in the last 20 years. They are (in order of hottest first): 2010, 2009, 1998, 2005, 2003, 2002, 2004, 2006, 2007, 2001, 1997, 2008, 1995, 1999, 1990, and 2000. In other words, every year since 2000 has been in the Top Ten hottest years list, and the rest of the list includes 1995, 1997, 1998, 1999, and 2000. Only 1996 failed to make the list (because of the short-term cooling). So the claim that “it hasn’t warmed since 1998″ has been false since 2002. This statement is even more pernicious because it deliberately and dishonestly ignores these many record-breaking years since 2004.
Cherry-picking can be played both ways. If I pick any year prior to 1998-2000 and connect with any data point from 2001 onwards, I get a warming trend. In fact, the only way a AGW denier could get their “no warming since 1998″ misrepresentation is to deliberately and consciously look at the curve, pick 1998 to start, and only compare it to 1999-2001. Any other long-term combination of the data shows warming. Thus, this distortion of the data that Will keeps repeating is not just a simple misreading of the facts. Since the meme is quoted from 2009, this means that the deniers were consciously and fraudulently trying to distort the data to suit their purposes. The fact that this lie keeps being perpetuated despite the fact that scientists have offered numerous corrections shows the AGW deniers have the same casual disregard for the truth that creationists do. Such practices demonstrate the absymal level of their scientific integrity, and speaks to the fact that AGW deniers are not climate scientists, but people with political agendas who cherry-pick data, quote-mine out of context, and use whatever lies and half-truths they need to support their cause. The parallel with creationists and other science deniers could not be any clearer.