Letter to The Editor: Three statements to guide us on climate

By Terry Hansen
Hales Corners, WI
(March 13, 2020)

There are three statements by major scientific organizations that provide a valuable lens through which to view the climate crisis.

“(T)he amount of rise in carbon dioxide levels since the late 1950s would naturally, in the context of past ice ages, have taken somewhere in the range of 5,000 to 20,000 years; we’ve managed to do it in about 60.” (National Oceanic and Atmospheric Administration)

Although Earth’s climate has changed before, it’s the pace of the current change that’s most troubling.

“Climate change resulting from anthropogenic CO2 emissions and any associated risks to the environment, human health and society, are…essentially irreversible on human time scales.” (Fourth National Climate Assessment, U.S. Global Change Research Program)

About half of the carbon dioxide we emit stays in the atmosphere for centuries or more.

The United States is the greatest cumulative emitter, with twice the historical emissions of second place China. Given the long residence time of CO2 in the atmosphere, this means the U.S. is responsible for a larger percentage of the current CO2 concentration than any other nation.

“Limiting global mean temperature increase at any level requires global CO2 emissions to become net zero at some point in the future.” (Global Warming of 1.5°C, Intergovernmental Panel on Climate Change)

Net zero carbon dioxide emissions means reducing emissions enough that they are balanced by CO2 removal, such as being absorbed by forests and dissolved in the oceans, otherwise the concentration of carbon dioxide in the atmosphere will continue to grow.