The Evidence for Global Warming: A Summary

 

Global warming is a controversial issue and I would like to take as dispassionate a look at it as I possibly can. First, I will summarize what I consider to be the main evidence for global warming and then discuss what this means for public policy.


Here is the evidence as I see it:

  • Greenhouse gasses (mostly carbon dioxide) in the atmosphere have been increasing since the beginning of the industrial revolution and have now reached approximately 400 parts per million.
  • Ocean heat content has been building steadily in recent years.  Warmer water means more evaporation into the atmosphere which means more precipitation around the world.
  • The extent of summer sea ice in the Arctic has gradually been receding.
  • A big chunk of sea ice (the size of Delaware) has just broken off the Antarctic Peninsula and is floating in the South Atlantic Ocean.
  • The sea level is rising at the rate of one-eighth of an inch per year which is equivalent to one foot per century. Globally, eight of the world’s ten largest cities are near a coast.
  • In the U.S. Spring is arriving earlier each year on average, especially in the Southeast.

Some of these phenomena may be beneficial such as more rainfall around the world and longer growing seasons. Less ice in the Arctic Ocean allows more summer navigation.  But rising sea levels will become catastrophic in low-lying coastal areas.

Conclusion. The above observational evidence for global warming is well established and hopefully non-controversial. The sources are scientific agencies whose integrity should be  beyond reproach. Once we accept the fact that global warming is for real and is caused by human activity, the question is what we should do about it.  This will be the topic of my next post.

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