Tuesday, January 20, 2015

Just a little bit warmer

Graph 1: Ascending: The global temperatures of my life. (data source: GISS)
Last Friday, NASA's Goddard Institute for Space Studies (GISS) released the final piece of data for 2014 global temperatures. The numbers are published in several places, and the newspapers pick them up almost instantly, but the page I've always used is http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt. It's a simple text page, and NASA's been using the same address for it since at least the 1990s. Sometime around the middle of each month, they just add another number, showing the final data for the prior month. And then I can look for myself, as is my preference.

I follow the data pretty closely, so I already knew that May had been the warmest May since the beginning of record keeping in 1880. I also knew that 2014 set new records in August and September, too. I knew that, when looking at records, even monthly records, it's pointless to look further back than 1998. And I knew with near certainty that the December numbers would confirm 2014 as the warmest year since record keeping began. Graph 1 is a graph I put together in excel showing the GISS annual temperature index, with a linear trend line.

Globally, warming has been consistent over the half century of my life. But warming is measured in increments we might consider "small." The GISS numbers are presented in hundredths of degrees celsius; the average yearly increment over the course of my life is barely one one hundredth of a degree. 20 times during my lifetime one year has been cooler than the one that preceded it. 1963 was warmer than 1976, by a substantial margin. Truncating the graph to 1976, I'd end up with this:

Graph 2: Look at this, it's flat! (data source: GISS)
I could use this graph and make a case -- admittedly not a particularly strong one, mathematically -- that there was no warming during my youth. I'd just have to cherry pick my end points, and conveniently ignore the outliers at each end of the graph: 1963 was the warmest year in that decade, and 1976 was the coldest year of the past half century (and remains the most recent year to end up colder than average).

By cherry picking data points, it's easy enough to make the data lie. More recently, the period of September 1997 through August 1998 shattered all previous records. 11 months during that 12 month period set monthly records, mostly by large margins. In just 2 years, global temperatures rose by 3 tenths of a degree; from 1985 through 1998 the difference was more than a half degree. That the winter of 1997-1998, fueled by a historic El Niño, was anomalous in absolute temperature terms isn't relevant to some; just that it can be used as a startpoint, as if it was a new normal. This leads to the inevitable new argument: It's not getting warmer anymore!

In some respects, that was briefly true: 2013, after all, was colder than 1998. Not by much, and not everywhere. But it was a touch colder. Never mind that 9 of the 10 warmest years on record have happened since 1998, the absolute number of the one data point was less, and the climate change deniers have been out in some force. Their links are easy enough to find.

But 2014's record warmth -- with no El Niño this time -- was as predictable as the sun rising in the East, and even cherry picked data points won't flatten the trend line anymore (note: with small data sets -- and 17 points is a relatively small set, one anomaly can throw the trend; just as having the start point in 1998 flattens things, so too would a single new "cold" year).

Graph 3: Even starting with El Niño, it's still getting warmer. (data source: GISS)
Then there's the local weather: How can there be global warming when it's 10 below outside? Indeed, where I live in Michigan, if I start with 1998 I can draw a trend line that's down rather than up.

Graph 4: That local trend line is down! (data source: Weather Underground)
I have written about local weather patterns before; after the brutal early spring of 2012 when the month of March averaged 16 degrees Farenheit above normal, and the subsequent return to normal temperatures that wiped out our tree fruit. The 3-month "Polar Vortex," itself caused by Global Warming, not only wiped out our crop for the 2nd time in 3 years, it also drove the temperatures as measured at Detroit's Metro Airport to their lowest annual levels in decades.

It's tempting to overread, more so when I look out my window. Living off the grid isn't an option. This isn't presented as a proof of anything, or even as "science," necessarily. That said, I hope that some recent trends toward science denial end sooner, rather than later. Seems to me the time for "debate" has passed.