Global warming stopped in 1998 and it has been cooling since then.
I am hearing this all over the place. What they then do is carefully pick the temperatures from individual years and compare them with other individual years to try and show a pattern that suggests cooling. There are three problems with this.
First, the possibility of cooling trends, locally or temporary, is quite likely within a general warming trend. Climate does not change linearly, but will vary up and down from year to year. This is why, as I will say again below, individual years are not significant. An individual year can include anomalies like El Nino or La Nina conditions. In addition, things like volcanic eruptions can cause temporary cooling (something deniers like Rush Limbaugh seemed to ignore when they used to claim, in the 1990's, that global warming was caused by Mt. Pinatubo). An initial cooling over Antarctica was predicted by the global warming models. This Antarctic cooling has been used by some deniers, who either don't realize or ignore that temporary cooling of Antarctica was predicted by the models, as "evidence" that global warming wasn't happening. Well, as predicted, that cooling trend has ended even in Antarctica. The only deviation from what was predicted by the models was the temporary cooling didn't last as long as predicted.
Second, there is a major error made by the deniers: you do NOT judge science based on selected data points. Only using a complete data set. The deniers cherry pick individual years to make their point. Scientists use entire data sets. When you do that, THIS is what you see:
These data show unequivocal warming. What the deniers are doing is sientifically dishonest. Let me use an example. According to NASA's Goddard Institute of Space Sciences (GISS...where, as a matter of fact, my wife works):
Climatologists at the NASA Goddard Institute for Space Studies in New York City said today that 2008 was the planet's coolest year since 2000.
This single piece of information is what deniers are basing their arguement on. But they fail to go on and tell you the rest of the story: (from the same report)
Yet this does not mean that global warming is no longer a threat, they said. The analysis also showed that 2008 was the ninth warmest year since continuous instrumental records were started in 1880. The 10 warmest years on record have all occurred between 1997 and 2008.
So the deniers claim the earth is cooling since 1998 even though the 10 warmest years on record have all been within the same decade they claim we are seeing cooling.
And the deniers don't tell you this:
the Earth's cooler temperature last year is due in part to the fact that the Sun is just passing through solar minimum, the low point in its 10 to 12 year cycle of electromagnetic activity, when it transmits its lowest amount of radiant energy toward Earth.
So there is an exlpanation for 2008 neing cooler. In fact, as no denier will tell you, there is a second reason as well:
Most of the world was either near normal or warmer in 2008 than the norm. Eurasia, the Arctic, and the Antarctic Peninsula were exceptionally warm, while much of the Pacific Ocean was cooler than the long-term average.
The relatively low temperature in the tropical Pacific was due to a strong La Nina that existed in the first half of the year, the research team observed.
So a cyclical minimum of solar output combined with a La Nina condition is BOUND to give you a cooler year. The global warming models would PREDICT that within a decade of the warmest temperatures on record you will still get cool years when you have a cyclical minimum of solar output combined with a La Nina condition. The year 2008 fits the models. Global Warming Deniers don't tell you that.
Finally, the deniers don't tell you that no scientist would EVER make a claim based on a single year. From the same article, quoting GISS scientist Jim Hansen:
"The rank has scientific significance in some cases, such as when a new record is established," Hansen said. "But rank can also be misleading because the difference in temperature between one year and another is often less than the uncertainty in the global average."
I am a scientist and I know you NEVER make a claim based on individual data points but ONLY using the entire data set.
A more detailed scientific debunking of this latest Global Warming Denial Lie can be found at the New Scientist.
Science is not opinion. It is based on observation of data. It is based on hypothesis tested by observation of data. Every single hypothesis offered by deniers has been shown to be wrong by the data. This is why not one single peer-reviewed paper has bene published showing evidence contrary to human-caused global warming. The theory still has points of contention, but the overall theory has been supported year after year by the data.
When you hear the deniers, remember that they have lied to you every year since they started opening their mouths. Pay attention to the scientists and the data, not the deniers.