(B) The report includes clear explanations of the scientific evidence in regard to specific justifications for not taking action on climate change very frequently made by those who oppose climate change policies. These justifications and responses to them include, for instance:
Scientists don’t know that recent climate change is largely caused by human activities?
Report says: Scientists know that recent climate change is largely caused by human activities from an understanding of basic physics, comparing observations with models, and fingerprinting the detailed patterns of climate change caused by different human and natural influences.
Direct measurements of CO₂ in the atmosphere and in air trapped in ice show that atmospheric CO₂ increased by about 40 percent from 1800 to 2012. Measurements of different forms of carbon reveal that this increase is because of human activities.
The recent slowdown of warming means that climate change is no longer happening?
Report says: No, recent weather is not evidence that warming is not happening. Since the very warm year 1998 that followed the strong 1997-1998 El Niño, the increase in average surface temperature has slowed relative to the previous decade of rapid temperature increases. Despite the slower rate of warming, the 2000s were warmer than the 1990s. A short-term slowdown in the warming of Earth’s surface does not invalidate our understanding of long-term changes in global temperature.
CO₂ is already in the atmosphere naturally, and so human emissions are not significant.
Report says: Human activities have significantly disturbed the natural carbon cycle by extracting long-buried fossil fuels and burning them for energy, thus releasing CO₂ into the atmosphere.
Variations in output from the sun have caused the changes in the Earth’s climate in recent decades.
Report says: The sun provides the primary source of energy driving Earth’s climate system, but its variations have played very little role in the climate-changes observed in recent decades. Direct satellite measurements since the late 1970s show no net increase in the sun’s output while, at the same time, global surface temperatures have increased.