Weather and Climate: What’s the Difference?
February 1, 2013
2012 was the year of extreme weather and 2013 is already looking like it will be runner-up, if it doesn't break 2012's records. Over the past couple of weeks here in Southern Ontario the temperatures have gone from -20 (windchill -29) Celsius, to a high of 12. As of right now the temperature sits at -9 (windchill -16). At the start of the week I was walking around in shoes. A couple of days later I had my winter boots back on. The U.S., along with the rest of the world, has seen its fair share of extremes over the past year as records were shattered in 2012.
From The New York Times:
While parts of China are enduring the harshest winter in 30 years, the Antarctic is warming at an alarming rate. In Australia, out-of-control bushfires are partially the result of record-breaking weather (new colors were added to weather forecast maps, to account for the new kind of heat). In the United States, where Hurricane Sandy devastated parts of New Jersey and New York and where extreme drought still lingers in the Midwest, the average temperature in 2012 was more than a whole degree Fahrenheit (or 5/9 of a degree Celsius) higher than average - shattering the record.
More from The New York Times:
Such events are increasing in intensity as well as frequency, Mr. Baddour said, a sign that climate change is not just about rising temperatures, but also about intense, unpleasant, anomalous weather of all kinds.
Here in Britain, people are used to thinking of rain as the wallpaper on life's computer screen - an omnipresent, almost comforting background presence. But even the hardiest citizen was rattled by the near-biblical fierceness of the rains that bucketed down, and the floods that followed, three different times in 2012.
The extreme weather of 2012 has raised concerns among scientists, who say that these events are linked to climate change. According to the National Climatic Assessment report released in 2012:
There is "unambiguous evidence" that the earth is warming. "Certain types of weather events," the panel concluded, "have become more frequent and/or intense, including heat waves, heavy downpours, and, in some regions, floods and droughts. Sea level is rising, oceans are becoming more acidic, and glaciers and arctic sea ice are melting."
The report makes it clear that the earth is warming and extreme weather events are occurring with increased frequency. But is extreme weather proof of a warming planet? Yes, and no. Let's get this out of the way: Weather is not climate. We'll start by looking at some definitions:
Weather is the mix of events that happen each day in our atmosphere including temperature, rainfall and humidity. Weather is not the same everywhere. Perhaps it is hot, dry and sunny today where you live, but in other parts of the world it is cloudy, raining or even snowing. Every day, weather events are recorded and predicted by meteorologists worldwide.
Climate in your place on the globe controls the weather where you live. Climate is the average weather pattern in a place over many years. So, the climate of Antarctica is quite different than the climate of a tropical island. Hot summer days are quite typical of climates in many regions of the world, even without the effects of global warming (Source).
All this means is that you can't point to a single weather event and say, "It was climate change". However, weather conditions can tell us something about the state of the climate. A warmer planet increases, "the chances of weather disasters" (Source).
Another point to note is that although scientists predict a warmer planet, certain regions could face harsher winters.
The unprecedented expanse of ice-free Arctic Ocean has been absorbing the 24-hour sun over the short polar summer. The heat in the water must be released into the atmosphere if the ice is to re-form this autumn. "This is like a new energy source for the atmosphere," said Francis.
This heat and water vapour will affect the all-important jet stream - the west-to-east winds that are the boundary between cold Arctic and the warm mid-latitudes. Others researchers have already shown that the jet stream has been shifting northwards in recent years.
This should serve as a reminder that while the global trend is a warming planet, that trend may not be evenly distributed. We shouldn't expect the global average temperature to increase in a nice straight line. There could be cold periods, but the overall trend is a warming planet.