Brady or Belichick, Weather or Climate?

A few days ago, Bill Barnwell of ESPN asked the question, "Who contributed more to the Pats' dynasty, Tom Brady or Bill Belichick?"

That's a great question to ask for barroom conversation because it is impossible to answer unambiguously and thus invites vigorous argument and debate.  One can play games like how many Super Bowls would the Pats have one without Brady or without Belichick.  It could be that the answer in both cases would be zero and that Brady and Belichick together add up to greater than the sum of their contributions.  Such an interaction is called synergistic.

Although it is not a perfect analogy, I thought of similar issues related to trying to tease whether or not weather or climate contributed more to a particular weather event or season.  For example, many people have been asking me if this season's snow drought is caused by climate change, a question that I loathe to answer because it is so difficult to disentangle weather and climate given our warming world. 

In reality, weather and climate are highly coupled and quite synergistic.  Extreme events are often weather events (e.g., heat waves), but those events may be more frequent, prolonged, and/or severe due to climate change.  If I invoke the Brady or Belichick analogy, Brady throws the 4th quarter comeback touchdown pass (weather), but Belichick creates the system that makes such a play more common (climate).  Perhaps under a normal coach, Brady has 20 4th quarter comebacks, but under Belichick he has 42. 

Which brings us to this winter.  The lack of precipitation this winter is clearly related to a very anomalous upper-level flow pattern.   In addition, it has also been unusually warm.  At the Salt Lake City International Airport, the mean temperature for this December and January was the 5th highest on record. 

Source: NOAA Regional Climate Centers

So, if we wanted to simply take sides in a barroom argument based on this evidence, one could argue that yes, it's been dry and warm, but there have been droughts in the past and this years warmth is not unprecedented.  The 76/77 winter was worse, and there have been years in the past equally warm, so this could just be weather or natural climate variability.  One could also simply say this is due to persistent ridging, and thus is consistent with such variability.  On the other side would be someone who argues that global warming is affecting the jet stream and shifting global temperatures to make the likelihood of such warm weather more likely.  Hence, what we are seeing this year is a reflection of global warming.  

I don't find either of these arguments very compelling because weather and climate are so intrinsically coupled, much like Brady and Belichick.  This is also why I HATE being asked how climate change affects a weather event.  As a scientist, I am interested seeing in depth analysis of historical observations and numerical simulations to investigate this problem, which is known as extreme event attribution (see the climate.gov article Extreme Event Attribution: The Climate Versus Weather Blame Game for more information).  Such studies assess how the likelihood of an event has changed in a warmer world.  The approach is not without its warts.  A lack of historical data and limitations of models sometimes create some issues, but provides insights that are not possible if two climate scientists simply sit in a bar and take sides.  For example, we might not be able to say that this winter was caused by global warming, but instead how much more likely (or potentially less likely) this winter was given global warming.  

"Potentially less likely" might seem unlikely (did I just say that?), but much depends on the question you ask.  A warm winter like we have had is almost certainly more likely today than it was 100 years ago.  The dice are loaded as I like to say.  On the other hand, it could be that the lack of precipitation is less likely.  That might sound crazy, but most climate models run for the last IPCC assessment report increase the average wintertime precipitation over northern Utah.   Thus, what is meant by drought is important.  The answers one might get might depend on if one is examining precipitation amount or snowpack water equivalent.  They also depend on how far in the future that you look as the response sometimes requires more warming to become detectable.  

None of this is to suggest that the climate is not changing and that the ski industry will be just fine at the end of the 21st century.  Change is happening.  Weather variability will give us some good snow years in the future, and Utah's colder, higher altitude climate gives us more resiliency than other regions, but during the coming decades, we are going to see the emergence of a dramatically different snow climate.