Tuesday, January 23, 2018

Weather or Not

We just learned that the year 2017 is the 3rd warmest year since modern recordkeeping of global temperatures.  It is not a “winner” year, so not really considered newsworthy after 2016’s record breaking.  However, 2017’s bronze medal finish masks the important observation that the four warmest years so far have all occurred in the decade that started in 2010 (see figure).  The decade before, 2000-2009 is the current record holder, which will undoubtedly be eclipsed by 2010-2019.  Such decadal trends are much better indicators of climate change than yearly or seasonal records  and, especially, weather.  

Annual temperature anomalies through 2017 relative to 20th Century temperatures. 
Credit: NOAA, https://goo.gl/vfMe8o

Cataloguing 2017 as the 3rd warmest year for the US seems to contrast with personal weather experiences.  Since December the US northeast has been battling bitter winter conditions, with very low temperatures and considerable snowfall.  Where is the warming, as President Trump tweeted at the end of the year?  Weather is the expression of short term, local condition of the atmosphere, or the “here-and-now”.  While weather is ultimately linked to climate, it only does so over long time period, not the current conditions, or the “now”.  Also, weather patterns are local, so one person’s cold snap experience is matched by another’s unusual heat, the “here” of weather. 

Confusing weather and climate also arose during 2017’s late summer hurricanes that battered the southern US and the Caribbean (notably Harvey, Irma and Maria).  Researchers, media and tastemakers alike were eager to blame global warming for the unusual and costly occurrence of several major storms in 2017.  But the evidence is again more complicated, as we also have had low storm cycles in recent, otherwise warm years.  Maybe next year we have another lull in storm activity, which no more characterizes climate warming, as high storm activity in 2017.  We know that, as the atmosphere and the ocean warm, more energy is available for the build-up of major storms.  But warming is a gradual and slow process.  Only as the 21st Century progresses do we expect to see more and/or stronger storms, but sequential years have little change on average.  A year without major storms, just like a cold period, is no more evidence for climate stabilization or cooling, than a year with great storm activity is evidence for climate warming.  This eagerness to conflate weather with climate in support of one’s favored argument feeds today’s contentious discussion, while clouding the urgency to address the impacts of a changing climate on regional and global scales.

Whether 2017 is a cooler year than 2016 and 2015, whether it is characterized by a cold spell, or by major storm activity must not affect the need to address the slow atmospheric, ocean and land warming that is taking place around the world.  The impacts of warming will be significant, if not calamitous for the unprepared, especially the less-developed equatorial nations and the poor of the world.  Reductions in greenhouse gas (GHG) emissions, as proposed by the 2016 Paris Accord, provide an admirable step in the right direction, but is not enough to stop or even slow gradual warming.  To achieve that, more aggressive emission reductions are needed, as a recent UN report showed (the 2017 Emissions Gap Report, https://goo.gl/JXHMv3), or through climate intervention.  The latter, more ominously called geo-engineering, aims to address the symptoms and roots of warming through solar radiation management of GHG removal, respectively.  Given that human society has been engineering climate through GHG addition since the mid-19th Century industrial revolution, perhaps climate retro-engineering is a more appropriate descriptor.  While weather is good watercooler conversation, it is not a good proxy for the climate change debate.  Whether or not the bronze medal for 2017 warming will become a gold medal for 2018, warming is underway, and we should aggressively deal with it, better sooner than later.

[Follow Ben van der Pluijm on Twitter: @vdpluijm]

1 comment:

Brause said...

Hi Ben,
1. Paul is turning 80 on the 27th. We are the only two of his PhD students getting away without handing in a geological map.

2. "Contrarians" (I try to be nice) do not only not distinguish weather and climate, but also regional and global, 2D and 3D (sea ice), and science and politics.
Science is more complicated than "the models are wrong" or "climate has always changed". Many of their logical connections are "non sequitur".

3. "Contrarians" use time scales favourable for deception: either the geological time scale ("...climate was different in the Ordovician...") or one since 1998...always creating something out of context.

4. The latest trick is compressing the Y-axis of the t-T diagram (see above). Bob's homework will be adding the average Ts for ice ages and warm ages to his diagram.

5. An example of 2.: climate is defined by 30-year intervals. Therefore, even if it is warming for 5 years, this may (but in this case isn't) part of a cooling phase. Anybody screaming warming has stopped in 1998 (which it hasn't), therefore global warming is over, is simply wrong.