A Record a Day Keeps the Apples Away!

December–February average temperature across global land and ocean surface

Click image for larger view.

This past year has seen great weather extremes.  The most prominent globally have been the record high temperatures as shown at right for the 2015-2016 winter.

For those of us in the US Northeast, one striking feature of this past winter is that our local regional experience was on par with the rest of the world!  February 2016 was the 10th month in a row in which each successive month broke the global high temperature record for that month.  February itself capped off this streak by being the hottest of them all, setting the global record for greatest departure from average temperature for any month in the instrumental temperature record (1880-present).

Click image for larger viewGiven those statistics, it follows that the 2015-2016 winter was a global high temperature record for the winter season, and most of the Northeast was one of the hot-spots breaking local regional records as well.  This is a strong contrast to the previous two winters when most of the world was indeed setting successively higher temperature records, but the Midwest and Northeast of North America were experiencing regionally cold winters from ‘regionally localized’ outbreaks of cold Arctic air.

These high global temperatures are clearly attributable to global warming.  The 2015 El Niño worked together with progressive global warming to determine the sheer magnitude by which all past high temperature records were broken. But 2015 was also much hotter than all the previous big El Niño years, such as 1997-98 and 1982-83. So El Niño contributed only in a supporting role.

Some Meteorologists and climatologists think 2016 may break the global high temperature record too: three consecutive record-breaking hot years in a row!  This is a wake-up call to all of us and a call for action.  The COP21 international agreements come not a moment too soon, and can only be ‘in time’ if all the nations fully implement and continue to strengthen the accords.

temp departure April 5In April, however, the Northeast was hit by a late-season outbreak of cold weather that swept across the north-central and eastern parts of the continent.  This is back to a story that we have been more used to in the past few years, where the rest of the world continues to simmer, but we are bundling up for cold.

Is this part of climate change too?  That is much less clear.  Some climatologists will say that we are experiencing more cold outbreaks than before because of global changes like the reduction of Arctic sea ice.  This shift from ice to open water in the Arctic ocean, some scientists say, is changing patterns of stable high and low pressure regions and jet stream behavior in a way that predisposes the weather to cold air outbreaks and other extremes.  Others, however, are not convinced that these regional effects are strongly related to climate change and consider the recent cold episodes to be part of the natural variability of the climate system.

This current April cold snap is due to a familiar weather pattern called a ‘Clipper System’ in which low pressure systems originating in western Canada move rapidly across the continent from West to East and bring sudden cold spells.  Clipper Systems are predominantly winter storm systems, however, and it is relatively rare to have such a strong one arriving as late as April.  Only continued observation and further study will give firm answers about whether these regional weather patterns themselves are being altered by global climate change.  Here’s what the record-breaking cold looked like in early April (above, right).

record lowsIthaca, NY, home to Cornell University, had its first below zero April temperature on record.  Other cold temperature records were set throughout the Northeast (right).

More damaging at times than simply warmer-than-average or colder-than-average temperatures are temperatures that fluctuate between extremes.  This year grape and tree-fruit growers in many parts of the Great Lakes, Northeast, and down into the Mid-Atlantic states will have damaged or lost fruit crops.

While the vines and trees are very cold hardy when dormant for winter, too much warmth in early spring causes the sap to flow and the buds to swell and the current-season buds become much more sensitive to cold.  Peaches, cherries and even apples have likely been damaged by the April cold weather.

Greg Peck, Assistant Professor of Horticulture, School of Integrative Plant Science, checks apple buds in mid-April. The brown, damaged tissue (circled) is a result of sub-freezing temperatures on April 5. Damaged flowers will not produce apples this year. Click image for larger view of bud damage.

Greg Peck, Assistant Professor of Horticulture, School of Integrative Plant Science, checks apple buds in mid-April. The brown, damaged tissue (circled) is a result of sub-freezing temperatures on April 5. Damaged flowers will not produce apples this year. Click image for larger view of bud damage.

Some regions in New York that may have escaped the worst include orchards and vineyards along the shores of the Great Lakes and other large water bodies. In such localities, the water bodies kept the March temperatures from warming up so fast, and thereby kept the fruit crops from breaking bud too soon in advance of the cold snap.  It will be some weeks before a full assessment of crop damages is made.

This highlights that one of the greatest climate perils in many cases is not simply record heat, or record cold, but less stable conditions that can vacillate from one extreme to the other.

And what’s next?  NOAA’s long-term seasonal forecast is for a very likely hot Northeastern summer!



Category: What's With the Weather

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