WEATHER AND CLIMATE

What are we to make of this winter’s weather so far? Central California has been seasonally mild and very dry. The eastern part of the country has seen repeated severe cold as has much of Europe and the Near East. Meanwhile, several southern hemisphere nations are suffering from intense heat waves.

In December, a powerful wave of cold and snow swept down across Lebanon and Israel, paralyzing those usually temperate places and causing snow in Cairo, Egypt, for the first time in 112 years.  The early January arctic blast that rolled over our nation’s Ohio River Valley and into New England broke records for all-time low temperatures.

At the same time, extreme heat in Australia is challenging that nation.  Early January there saw temperatures rise to over 120° Fahrenheit and a huge flock of heat-killed bats fell dead from the sky. Argentina, another southern nation, has also been suffering from intense heat.  The demand there for electricity to run air conditioners has recently overwhelmed at times the nation’s power network.

Meanwhile, in Antarctica, where it is theoretically summer, a Russian research ship found itself trapped in sea ice for two weeks before it finally broke free.

Extreme weather always generates discussion, and in these polarized times such talk drifts quickly into arguments about climate change.  If I am to believe what I hear on the radio, the weather in our own eastern states clearly proves that climate change is a hoax. In Australia, and Argentina, of course, the weather proves exactly the opposite to many residents.

In the face of all this chatter, we might do well to step back and look at larger patterns. A good starting place is an old saying – “climate is what you expect, but weather is what you get.”

What this means is that climate represents averages while weather is what happens daily. Here’s a local example: during the seven-month “rainy season” in Visalia, the average daily rainfall is about .05 inches. But as we all know, it doesn’t rain every day. A storm with an inch of rainfall thus provides us with 20 days of average precipitation. The fact that 19 of those 20 days may have been dry doesn’t change the climate statistics.

Individual, local events featuring short-term extremes of heat and cold neither prove nor disprove climate change. They are simply “weather”  — by its nature a short-term phenomena.  Instead, we need to study climate, that is long-term averages. We also need to look for changes in the frequency of extreme weather.

When we do these things, we discover two fundamental facts. The first is that long-term temperature averages continue to creep upward. In California, for example, annual temperature averages now run two to three degrees warmer than a century ago. This is why our Sierra Nevada glaciers are melting.

The frequency of extreme weather is also increasing – both hot and cold. This is in line with climate-change models that predict that a planet that is warmer overall will have more powerful weather events.  The key to this is quite simple: all weather is driven by atmospheric heat. When there is more heat, more powerful things happen more often. 

What I am saying is that all the recent extreme weather — whether it be cold or heat, flood or drought – are reflections of the same thing: a measurably warming planet.  Drought in Central California, killing heat in Australia, and life-threatening cold in the American mid-west are all related.

So here’s the challenge – we all need to pay more attention to climate and get less excited about weather.  The extreme events of the past year or two will likely become more and more common in coming seasons.  Right now that means living with drought in Central California. One of these days, it is just as likely that we will be wrestling with flooding. Welcome to a warmer planet.

© Wm. Tweed