Why we have global warming?

What we know — and what we don’t — about global warming
October 20, 2015 – 07:15 am

NORTH MIAMI, FL - MARCH 14: Buildings are seen near the ocean as reports indicate that Miami-Dade County in the future could be one of the most susceptible places when it comes to rising water levels due to global warming on March 14, 2012 in North Miami, Florida. Some cities in the South Florida area are starting to plan for what may be a catastrophic event for the people living within the flooding area. Climate change. (Photo by Joe Raedle/Getty Images)Editor’s Note: Last year was officially the hottest year on record, according to NASA and the National Oceanic and Atmospheric Administration. Yesterday, the American Meteorological Society delivered more bad news in a report on the state of climate in 2014. Greenhouse gases continued to climb, sea surface temperatures and the global sea level hit a record high and the number of tropical cyclones increased.

Gernot Wagner and Martin L. Weitzman, co-authors of “Climate Shock, ” argue that we should insure ourselves against climate change. With a 10 percent chance of temperatures rising 11 degrees Fahrenheit or more and the catastrophic damages that could occur as a result, why wouldn’t we? Below, they lay out their case for pricing carbon dioxide pollution and discuss the economic consequences of a warming planet. Watch Thursday’s Making Sen$e segment for more on the subject.

150213150217150217The economic options for combatting climate changeAs greenhouse gases accumulate and global temperatures slowly rise, what can we do to insure against the catastrophes of climate change? Economics correspondent Paul Solman talks to the authors of9VMR-S3jTzI

Two quick questions:

Do you think climate change is an urgent problem?

Do you think getting the world off fossil fuels is difficult?

This is how our book “Climate Shock” begins.

In fact, it’s not our quiz. Robert Socolow from Princeton has posed versions of these questions for a while. The result is usually the same: most people answer “Yes” to one or the other question, but not to both. You are either one or the other: an “environmentalist” or perhaps, a self-described “realist.”

Such answers are somewhat understandable, especially when looking at the polarized politics around global warming. They are also both wrong. Climate change is incredibly urgent and difficult to solve.

What we know is bad

It doesn’t take much to imagine what another foot or two will do. And sea levels at least 20 feet above where they are today? That’s largely outside our imagination.

This won’t happen overnight. Sea levels will rise over decades, centuries and perhaps even millennia. That’s precisely what makes climate change such an immense challenge. It’s more long-term, more global, more irreversible and also more uncertain than most other problems facing us. The combination of all of these things make climate change uniquely problematic.

What we don’t know makes it potentially much worse

Climate change is beset with deep-seated uncertainties on top of deep-seated uncertainties on top of still more deep-seated uncertainties. And that’s just if you consider the links between carbon dioxide concentrations in the atmosphere, eventual temperature increases and economic damages.

Increasing concentrations of carbon dioxide are bound to lead to an increase in temperatures. That much is clear. The question is how much.

The parameter that gives us the answer to this all-important question is “climate sensitivity.” That describes what happens to eventual global average temperatures as concentrations of carbon dioxide in the atmosphere double. Nailing down that parameter has been an epic challenge.

Ever since the late 1970s, we’ve had estimates hovering at around 5.5 degrees Fahrenheit. In fact, the “likely” range is around 5.5 degrees plus-minus almost three degrees.

Source: www.pbs.org
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