Standards For Declaring That The Climate Has Changed…A Discussion
Today I saw the following message from Dr. Daniel Swaim that got me thinking:
There are no true standards for declaring that the climate has changed in a given area on the planet or at an individual city or site as far as I know, which is a little surprising to me given where we are in 2019. We do know that the climate has warmed in just about every nook and cranny on the Earth’s surface since the 1800s, but at what point can we declare that the long term climate has changed or changed to the point of being very detrimental? When an area gets beyond +.5C above long term averages? +1.0C as has just happened across the globe?
Perhaps climate has changed when traditional flora and fauna have can’t adapt, undergoing stress. Many of my coworkers at The Weather Channel used to tease me that climate change would have not occurred in Atlanta unless pines were replaced by palms. They had a point. And yes, it has not warmed so much that our average of about 2″ of snow since the mid 20th century has diminished to 0.
Across the American West, though, climate change has begun to denude great tracts of forest as indicated by Daniel’s tweet. The tree line is climbing across mountainous areas worldwide. The Sahara is shifting southward, and tundra areas are melting, but can climatologists agree on a standard to declare that areas within those vast regions have undergone climate change? Not yet, and so we need to discuss this topic.
Perhaps the easiest symptom to diagnose, as Daniel hints at, is drought. Let’s say that the long term precipitation average at station X is 50″ a year. Let’s also say that a certain tree growing near station X needs at least 40″ a year for survival. Over the next several years average rainfall at station X is 35,” not enough to sustain that certain species of tree. There are standards for declaring that station X is in a drought, in fact we have several different declaration states up to “extreme.” Now, when does “extreme” drought or a lesser value for drought become the norm? When would Station X be declared from moving from a moderate climate for rainfall to an “arid” climate? Would this “drought” need to go on for 5-10 years or much longer? What if after 10 years the rains came back enough to bring back those trees at station X? At what point going back to Daniel’s tweet can a drought be declared over for lack of rain, not more?
So, you see how nebulous from my brief essay how difficult any declaration that climate has changed can be, or even what constitutes an extremely long period of drought. I whole heartedly agree with Dr. Swain on this. Perhaps some sliding scale needs to be developed based on the difference between rising temperatures, changes in precipitation, time, and long term averages. Elevation of a station would be a factor.
Standards are needed because the public is confused enough as is on the issue of climate change. Usually numbers and definitions lead to more clarification, not less.
If you are interested in giving your two cents on definitions and standards for climate change drop me a note. Perhaps this would be a good discussion for Twitter. Thanks in advance!
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The Climate Guy