One of the frustrating aspects of the ‘climate change’ debate is the confusion between two frequently used terms — ‘weather’ and ‘climate’. NASA distinguishes them this way: Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere “behaves” over relatively long periods of time. Some wag said that climate is what you expect, weather is what you get. You won’t find much more helpful definitions than these. Conventionally, ‘climate’ is the average over thirty years. ‘Climate change’ is therefore conventionally defined as what we learn by comparing thirty-year periods. Unfortunately, we don’t have many of these periods that have useful data.
And I would argue that real climate change occurs over much longer periods. I read an absorbing account of particular changes recently in the Newsletter of Risk Frontiers at Macquarie University, in an article about paleoclimate datasets that suggest a climatic reason for the Polynesian colonisation of the Pacific: over long periods (a century or two) general wind directions changed to favour sailing in particular directions. Or, to use an example I have used in the past, two thousand years ago Rome depended on wheat fields in northern Africa for the basic food of the Roman Empire— bread. I’ve been to those wheatfields in Libya. Today they are simply desert sand, though the striking Roman stone reservoirs are still there, 2000 years later.. The Sahara was much wetter in the past. So was inland Australia, where Aboriginal cave paintings depict lakes, fish and waterbirds.
To me that is real climate change. What we see today, on the evidence, is just weather. It’s not even ‘extreme weather’, or ‘climate disruption’. It is understandable that people find it difficult to know what is happening. It doesn’t really matter what is happening in weather — heat, cold, rain, drought, floods, storms, fires — there will be an AGW scaremonger telling us all that this is just the climate change he or she or they have been warning us about. And it works. Many people accept the scare. But you need to look hard at the evidence. Here are two home-grown illustrations of the difference.
Example 1. The current el Nino has produced higher temperatures for many parts of the world, including Canberra, where all four months this year have had higher-than-average temperatures. The el Nino is subsiding quickly, and it may be followed by a cool la Nina, with rain. It may not. We will see. But these conditions are aspects of our weather. There have been el Ninos for hundreds of years, and there will be more in the future, almost certainly. There is no reason at all to suppose that variations in the Southern Oscillation Index (SOI), which is another way of measuring the el Nino/laNina movements, are caused by greenhouse gas emissions. El Ninos and la Ninas are weather, as is the heat, or rain, or cold, or droughts or floods that accompany them.
Now those who live in the national capital know that it is time to put the central heating on when Anzac Day come. In our case it would have been April 26th, but we were away for two days. While we were away our house became cold, and on our return we turned the heating on. The fact that we had had unusually warm weather for the summer and autumn of 2016 made no difference. The reason is related to climate, not weather. At this time of the year, on every day, sunrise comes a minute later, and sunset a minute earlier. Over a week that is 14 minutes less sunlight, assuming that the sun shines all the time. Over a month that is an hour a day less sunlight. The sun is less powerful in April than it was in March, as its incidence is lower. The houses cool down; the nights are colder; the days have less sunlight. That will continue until June 22nd, when the days will start to become longer, and the cycle reverses. Weather can have local effects. Last year there was a very cold day on April 6th, and returned on the gas fire in the living room. But the central heating wasn’t needed until just before Anzac Day. That is climate at work. The ambient heat of our house just declines because there is less sunlight, and less heat.
Example 2. I went to a concert at the Canberra International Music Festival given by Katie Noonan and the Brodsky Quartet. Before one of the songs she paid a tribute to an audience member who has been trying to persuade Australia’s politicians that they should do more to combat climate change. Canberra’s temperature today was 25 degrees, she said. That’s not normal! Tell them that! She was partly right: that was a warmer day than usual, but by no means unprecedented. The average maximum temperature for April in Canberra is 20 degrees Celsius. The next day was cold, very windy and wet. Wind chill around 8 degrees. Way lower than normal. Two days later we had our first winter day, with a very cold night and a cold wind throughout the day. At least it was sunny. Katie Noonan is a fine singer, with a wonderfully varied voice, but she doesn’t understand the difference between weather and climate. Most people don’t, so she’s normal, and her lack of understanding is not unprecedented.
In truth, all the talk about ‘climate change’ is misguided. What the Climate Botherers are talking about is variations in weather. We get lots of them, and one can usually find the cause. Wikipedia sets out five ingredients of weather and climate:
- Temperature is how hot or cold the atmosphere is, how many degrees it is above or below freezing. Temperature is a very important factor in determining the weather because it influences or controls other elements of the weather, such as precipitation, humidity, clouds and atmospheric pressure.
- Humidity is the amount of water vapor in the atmosphere.
- Precipitation is the product of a rapid condensation process (if this process is slow, it only causes cloudy skies). It may include snow, hail, sleet, drizzle, fog, mist and rain.
- Atmospheric pressure (or air pressure) is the weight of air resting on the earth’s surface. Pressure is shown on a weather map, often called a synoptic map, with lines called isobars.
- Wind is the movement of air masses, especially on the Earth’s surface.
We don’t have good data for Australia for any of these variables, but what we do have do not, at least to me, show any sign that some kind of climatic change is happening. Temperatures have had highs and lows in the past — right back to the landing in 1788 and in the years that followed that event. Precipitation follows the SOI. There’s been no obvious increase in storms, fires or other so-called ‘extreme’ events. Yes, the costs of these events has risen, but that’s because there are more people, living in more places that are vulnerable to storms and fires.
In my opinion we should stop taking about ‘climate’ except when we are referring to large changes to large areas for which there is really good evidence, and stick to ‘weather’ as the common term for what we experience. As I have argued in earlier essays in this set, projected ‘extreme’ weather in the future is hardly worth considering, because it is based on projections from computer models that cannot even predict temperatures over the next few years..