Monday, January 5, 2015

Where is climate change headed?

With the completion of yet another circle around the sun, it's time to take stock of where we're headed with global climate.  I'm going to do something that is somewhat risky—extend statistical models beyond the data range that was used to create them, but necessary if we want to see where current trends will take us in the future.


First up: Global temperature.  I've already gone over the evidence showing that the so-called "pause" does not exist and that the trend since 1970 remains unchanged.  Using the coverage-corrected HadCRUT4 data set of Cowtan and Way, here is where we'd expect global temperatures to be through 2030:

Figure 1.  Observed and projected trends in global temperature anomaly.  The thick black line is the observed trend up through 2014 year-to-date.  The thick dashed red line is the projected trend from 2015 to 2030.  The thin dashed lines on either side of the main trend line are the 1σ and 2σ standard deviation lines, respectively. 
Extending the trend out into the future shows that the global temperature anomaly in 2020 should be 0.73ºC (2σ range: 0.54ºC to 0.92ºC) and 0.91ºC (2σ range: 0.72ºC to 1.09ºC) by 2030.  The year-to-date anomaly for 2014 (Jan-Nov) is currently 0.609ºC (second highest on record for the coverage-corrected HadCRUT4 data set), so if the trend continues, global temperatures are expected to soar over the next 16 years.  For what it's worth, the predicted temperature anomaly for 2015 is 0.64ºC (2σ range: 0.46ºC to 0.83ºC), which would make 2015 the hottest year in this particular data set.

Second: Arctic sea ice.  For this one, I combed through the daily satellite data to find the lowest sea ice extent for each calendar year.  I then fit a quadratic regression to the data and extended it out until the trend reached zero.  The end result?

Figure 2.  Minimum Arctic sea ice extent per year.  The thick black line is the observed trend up through 2014 year-to-date.  The thick dashed red line is the projected trend from 2015 to 2030.  The thin dashed lines on either side of the main trend line are the 1σ and 2σ standard deviation lines, respectively.
This is one prediction I really hope turns out to be wrong.  If the current trend continues, sea ice extent will reach zero by September 2034 (2σ range: September 2030 to September 2038).  The predicted minimum for September 2015?  3.99 million square kilometers (2σ range: 3.02 to 4.96 million square kilometers).

Third: Carbon dioxide.  This is the monthly Mauna Loa record from March 1958 to November 2014.

Figure 3.  Mauna Loa carbon dioxide levels.  The thick black line is the observed trend up through 2014 year-to-date.  The thick dashed red line is the projected trend from 2015 to 2030.  The thin dashed lines on either side of the main trend line are the 2σ standard deviation lines.
This one is very straightforward.  At today's rate, the yearly average (as represented by the trend) will reach 434.89 ppmv in 2030, with a maximum value in May that year of 439.05 ppmv.  That will lock us into at least 1.91ºC of warming above pre-industrial temperatures.  For 2015, the predicted yearly average is "only" 399.37 ppmv with a May maximum of 403.34 ppmv.  The year 2016 is when I expect the yearly average to cross the 400 ppmv mark for the first time in the history of Homo sapiens sapiens.

In short, climate is headed toward a state of more CO2 in the atmosphere, hotter temperatures, and less Arctic sea ice.  Just as anyone who does not get their "news" from Fox News would expect.

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