Tuesday, January 7, 2014

Weather? Climate? Confused?

Have you noticed the attention the weather has been getting in the media?  The cold blast for much of the U.S. & Canada, the trapped ship in the Antarctic, and the storms hitting Europe around Christmas are just a few examples.  Other news reports that you may not have been aware were the floods in southern Brazil and in the Caribbean, the heat wave in Argentina, the usually cold weather in the Middle East.  These are all weather events.

Some media outlets are reporting the cold events indicate that we have little to fear from global warming.  Yet global warming does not cancel the seasons.  In fact what we know about our changing climate is to expect more weather extremes worldwide.   Not just heat waves, but more floods, droughts, and even energized storm systems.  This is how a changing climate translates into daily weather.

Often many in the media confuse the difference between weather and climate.  Don’t worry, because some meteorologists do too.  The weather is basically composed the events that unfold in the present.  Meanwhile climate looks at the long term average of weather.  By definition this is a 30-year period.  We can look at shorter term trends to look at how changes are progressing, but we still have to look at the climate period of 30 years.

There has been much written about a pause in global warming however, all of these claims cherry-pick the data to start at 1998 which was an unusually warm year caused by a record El Nino.  The blogger Tamino at Open Mind has looked at the record statistically and has some good post here and here.  Stefan Rahmstorf at RealClimate.org also has an excellent post on the surface temperature record.

Global surface temperatures since 1970 with the trend line.  The trend has been a warming of 0.17°C/decade. The year 1998 was extremely warm due to El Nino.  Click on image for a larger view.  Image Credit: Dr. Marshall Shepherd.

Each year the global temperature is affected by natural and man-made components of the environment.  The natural components include insolation (incoming solar radiation), volcanic activity, the planetary orbital cycles, and oceanic cycles.  The man-made component includes the burning of fossil fuels, deforestation, and aerosols (like soot).  These change every year and help create the variability we see over the long-term.

Global warming is a climatic event while the cold temperatures we are experiencing are a weather event.  The cold weather is real and global warming is real.  In fact, the preliminary information indicates that 2013 was the 4th warmest year on record.

The temperature anomaly for the lower troposphere in 2013.  Preliminary information is that it was the 4th warmest on record for the satellite era.  Click on the image for a larger view.  Image Credit: nsstc.uah.edu.

Is there a connection between climate change and the cold weather we are experiencing?

There could be.  Recent studies indicate that the warming Arctic is leading to a phenomenon known as warm arctic/ cold continents.  A paper was just published indicating that the phenomenon is becoming more common.  We saw a similar event in December, 2010.

Bottomline: Cold outbreaks are not new.  What is news is that this is the coldest in recent memory which is why we have records.  Weather events occur in the context of climate, but single events do not determine climate.  As Dr. Marshall Shepherd is fond of saying “weather is your mood, climate is your personality”.  Your mood changes for day-to-day, but your personality lasts a long time.