Why Very Nice Weather Is Scary

My St. Albans,  Vermont yard Tuesday as the thaw
really took hold. 

If you're outdoors and it's partly sunny and 77 degrees, you should not be scared of the weather. After all, such weather sounds pretty pleasant.  

If you were in Bennington, Vermont yesterday, February 21, you experienced just that kind of weather. Note I said Vermont. In February. You can see why such weather in this case can be a little unnerving.

The weather extremes keep getting more extreme. A few years ago, I would have said it's pretty much impossible to get to 70 degrees in Vermont in February.

Then, yesterday, it was in the upper 70s. And we've now had two Februaries in a row in which it has been in the 70s in Vermont. The winter before that, it was 70 degrees in Vermont on Christmas Eve.

I keep telling you that a weather event on one dot on the map like Vermont does not tell you much about climate change. That is still true.

Yet, the entire East Coast was baking yesterday.

No fewer than 21 cities in the eastern United States from Florida to Maine broke records Wednesday for their hottest temperature on record for any February date.  Wells, Maine; Manchester, New Hampshire and Bennington, Vermont all hit 77 setting February statewide records across northern New England.

Tampa, Florida also hit an all time February record high of 89 degrees this week.

Same spot as above, 24 hours later. 

The weather extremes here in the Green Mountain State seem like they're getting more extreme and more frequent. That wouldn't be that big a deal except the extremes are getting more and more wild across many if not most parts of the world.

Of course, the trouble is, how do you measure the frequency of extremes. The overall temperature of the Earth is rising. That's relatively easy to measure. (NOAA just said that January for the Earth as a whole was the fifth warmest on record. And that means the Top 5 warmest Januaries have all occured since 2007.)  

Climate scientists tell us global warming will cause greater weather extremes. Anecdotally, that's easy to see. In addition to Vermont's February roast, a persistent stalled fetch of deep moisture is once again drowning parts of the Gulf states and South in flooding. The temperature is about to go above freezing at the North Pole like it's done a few times in the winter in recent years, which is very odd.

Arctic ice extent is at record lows for this time of year, and a bitter cold wave is heading toward western Europe from Siberia.

One way to look at the frequency of extreme weather is by examining warm spells, like the kind we just experienced yesterday.

Back in 2014, before many of the latest big, big heatwaves, Real Climate said record hot months at stations around the world were outpacing record cold months by a five-to-one margin. You can infer from this the world is warming as an unchanging climate would produce roughly equal numbers of hot and cold months.

An incredible  36-month streak of daily record maximum records exceeding daily record low minimums at weather stations throughout the United States ended in January, where record lows slightly outpaced record highs.

We're back to our old tricks, though. So far this month, U.S. weather stations have seen 1,707 daily record high temperatures versus just 174 record lows. Also so far this February, 37 weather stations have recorded their all time highest temperature for the month of February while just one recorded an all-time record low.

Another way to look at extreme weather events and trends in those events is the growing field of attribution science.

As Annie Sneed explained in Scientific American last year, computer programs are getting better at simulating the cause of extreme weather events, then estimating what would have happened without climate change. I'd better let her explain it:

"In our experimental set-up, we simulate the event in today's world, and then we remove anthropogenic emissions from the climate model's atmosphere, and do the same experiment again.  ...... Assuming everything else being equal, what is the influence of greenhouse gas emissions?"

This is all great, of course, but still, is there a way to measure the number of extreme events, say 100 years ago, compared to now?

I haven't come across such statistics, but I wish they existed.

Every time something extreme happens in the weather, climate change denialists and skeptics will point to a similar extreme in the past.

Yes, wild weather has always happened and always will, with or without climate change. Yes, it was in the 70s in New England yesterday, but it was 120 in the Great Plains in the summer of 1936.

However, are big hot spells more frequent than they were early in the 20th Century? The denialists and skeptics won't answer that question.

Muddying things further, some extremes that happen are just bad luck and have nothing to do with climate change. Or they would have happened anyway, but were possibly or probably made worse by climate change? How do you measure and prove that?

The consensus among scientists is that weird weather, like yesterday's summery February East Coast heat wave, is becoming more frequent with climate change.

The February heat wave wasn't as harmful as some big extremes, though budding flowers and crops up and down the East Coast will probably fall victim to normal spring freezes. In the past, if it got cold in March, who cares because plants hadn't started blooming yet.

Now we're getting these weird hot spells. California had a record warm winter, forcing crops and trees to start blooming too early. Then the inevitable winter frost and freeze hit last week.  The states $5 billion almond industry was almost certainly damaged by this.

Last year also had record February heat along the East Coast. Cherry blossoms in Washington DC bloomed too early, then many of the blooms were zapped and killed by a March freeze. Those blossoms are starting to bloom again this year, way too early. Will the same thing happen again.

As nice as this week's incredible February warmth felt to many of us, any weather extreme is bad, as I've just outlined.  And if extremes are getting wilder and more frequent, there's lots of trouble ahead.

Which is why I was scared yesterday when it was a very pleasant 77 degrees in Bennington, Vermont yesterday. In February.  Even as, exactly 24 hours later, Bennington was right back to normal February conditions: 30 degrees with fairly heavy snow falling.