Weather is the rain, snow, sunshine, or wind you can see happening right outside the window. It also includes all kinds of measurements such as temperature and humidity. It’s immediate and it’s exact.
The difference between weather and climate is that weather is what you can see happening. Climate is what you’d expect to see that time of year and throughout the year. If you’re planning to visit Canada next week, you’d check out what the weather is right now and the weather forecast for the region, so you’d know what clothing to pack. If you’re planning to move to Canada, you’d check out what the climate is for the region.
You’d expect a different type of prediction from a weather forecast than from a climate prediction. When you’re looking for a weather forecast, you want the exact weather it’s going to be tomorrow or next week. You don’t want to know if it usually snows this time of year. You want to know if it’s going to snow tomorrow.
That means different mechanisms are involved in predicting weather and climate. The types of uncertainties involved in weather prediction and climate prediction are also going to be different. The science of weather prediction is called meteorology. The science of climate prediction is called climatology.
Weather prediction
When trying to predict the weather, a meteorologist starts by looking at what’s already happening in the area. Is the barometer rising or falling? What is the temperature and wind direction? What are the clouds like? That can usually tell you the weather that’s coming later today or tomorrow.
If you’re looking for more accuracy of a longer-term prediction, check the conditions around the area. Weather offices get detailed information from ground stations across the entire country. With modern weather satellites, it’s easy to see what is happening across the country and out in the oceans. When you can see the loops of the jet streams, you can also see the kind of weather that’s coming your way, although you can’t always tell how fast it’s going to come.
Most modern weather predictions do pretty good for tomorrow, so-so within a week, and can even do decently a couple of weeks into the future. By taking larger factors into account, such as the Bermuda High, the amount of Siberian snow cover, and if there’s an El Nino or La Nina, weather predictions can even make a stab at guessing what the general weather’s going to be like next month, which path a hurricane is going to take, or even how many hurricanes there are going to be this year.
However, weather prediction can never be completely exact because it’s about trying to predict what is going to happen in unstable systems. Even when there’s storm clouds building up, it’s anyone’s guess if they’re going to release the rain here or in the next county. That’s why weather forecasts which include rain or snow are usually phrased as a percentage chance.
Climate prediction
Climate prediction isn’t about that kind of exactness. Instead, by averaging the last ten years of weather records, climatologists can say with confidence what kind of weather is typical for the region at any time of year. To go beyond that, climate prediction looks at cycles and trends.
Climatologists begin by using lots of weather data to identify large-scale cycles. These cycles take a very long time to complete. Even a short-term climate cycle like the El Nino ocean current still takes a couple of years. Long-term cycles like the North American Oscillation can take decades, centuries, or even millennia to complete.
Climatologists can use these cycles to predict what the overall weather is going to be like when a particular cycle is at maximum or minimum. They can also make educated guesses about how typical weather for an area is going to change in the future. However, it’s difficult to identify the effects of each cycle individually because they all interact with each other. Climatologists are still identifying new cycles and trying to figure out how they work with other cycles.
It would be completely impossible to do with only a few years of modern weather records. Weather records don’t go back far enough. Luckily, there’s all kinds of built-in weather records in nature. Tree rings permanently record how good each growing season was. Glacier ice cores record the amount of snow each year, as well as unusual amounts of ash or dust or trace elements in the air. Dozens of other types of natural weather records exist.
Strange weather doesn’t matter to climate cycles unless it becomes the norm. An oddball storm or unseasonable frost is always possible. Most years have some weird weather. However, it doesn’t become climate unless specific types of weird weather happen most years, so that they’re almost predictable.
For example, winter in southern Canada is usually cold with a decent amount of snow. However, there is usually a thaw in late December or the first week of January. It surprises newcomers, but that thaw happens so often that it is part of the normal climate. It’s perfectly normal and perfectly explainable. It has to do with what’s happening in northern Siberia at the same time. When Siberia is covered in snow, it creates deep waves in the jet stream. When those bends reach Canada, they pull up warm southern air, which creates a temporary thaw. But right behind the bend which pulls warm southern air north, the next part of the bend is going to pull down cold air from the Arctic again. After the January thaw, you can expect some of the coldest temperatures of the entire winter.
A climatologist can’t tell you that it’s going to go up to twelve degrees above freezing next Tuesday. That’s a job for weather forecasting. A climatologist can only say that something like this usually happens around this time of year and why it happens.
However, lately that thaw has been getting warmer and warmer. This year, it set record highs, breaking the record highs from just three years ago. The prairies still get that massive dump of freezing cold air from the Arctic after January from that jet stream bend, but the bend doesn’t move as much. The result is that the Yukon to the west and Labrador, Baffin Island and Greenland to the east keep getting unseasonably warm weather most of the winter, while the centre of the continent freezes. It also seems to be linked with a lot of nor’easters, because the jet stream just doesn’t move and keeps pulling storm after storm up along the east coast. During December 2010 and January 2011, Maritime Canada had five serious nor’easters in five weeks.
When weather records don’t fit the known cycles, climatologists try to find out why. Usually it means that there is another cycle or other factor which isn’t being taken into account. The global warming theorists believe that the new factor is an increased amount of CO2, methane, and other greenhouse gases in the atmosphere. Others think that it has to do with a previously unidentified solar cycle. It could even be both of those, or something no one has guessed yet.
Conclusion
Climate is the kind of weather you expect to happen in an area. Climate prediction tries to guess how weather is likely to change over the next year or more. It does not attempt to predict what is going to happen on any given day. Its measurement scale is too large for that.
Weather is what is actually happening now. Weather prediction uses what is happening now in many places to guess exactly what will happen a few days from now. However, weather prediction gets less and less accurate the further ahead you go. Its practical limit is about a week. Its measurement scale is too small for anything more.
