evidence: Myth No. 1: What global warming? Earth has actually been cooling since 1998. Some people skeptical of global warming claim that Earth’s global surface temperatures have been falling or have leveled off since 1998. They point to data now several years out of date from U.K. researchers that put 1998 as the warmest year on record. They also point to an unusually cool summer in North America in 2009 followed by an abnormally cold winter across the northern hemisphere. People who had to shovel record snows from their driveways or live without power during ferocious snowstorms in the northeastern United States began to doubt decades of scientific evidence on global warming. [...] People who dispute evidence of recent global warming sometimes point to two episodes in the past 1,000 years called the Little Ice Age and the Medieval Warm Period — times when northern hemisphere temperatures were higher or lower than average for decades or even centuries — as examples of internal variability, a kind of natural randomness in the climate system that can’t be explained by any specific forcing. If true, perhaps internal variability could explain the current rapid global warming, skeptics argue. In other words, maybe our current warming is just an unlucky roll of the dice, a blip rather than a long term trend.