Arguments
The difference between weather and climate
What the science says...
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Weather and climate are different; climate predictions do not need weather detail. |
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Climate Myth...
Scientists can't even predict weather
...Since modern computer models cannot with any certainty predict the weather two weeks from now, how can we rely upon computer models to predict what the Earth's climate might be like a hundred years from now? They can't! Yet people like Al "Carbon-Credit" Gore want you to believe that these models can predict the future. I bet I can do at least as well with a crystal ball (source: Kowabunga)
This claim is based more on an appeal to emotion than fact. The inference is that climate predictions, decades into the future, cannot be possibly right when the weather forecast for the next day has some uncertainty.
In spite of the claim in this myth, short term weather forecasts are highly accurate and have improved dramatically over the last three decades. However, slight errors in initial conditions make a forecast beyond two weeks nearly impossible.
Atmospheric science students are taught "weather is what you get and climate is the weather you expect". This is why this common skeptical argument doesn't hold water. Climate models are not predicting day to day weather systems. Instead, they are predicting climate averages.
Figure 1: Record highs are an example of extreme weather, but an increase in record highs versus record lows is a symptom of a changing climate. From Meehl et al. 2009.
A change in temperature of 7º Celsius from one day to the next is barely worth noting when you are discussing weather. Seven degrees, however, make a dramatic difference when talking about climate. When the Earth's AVERAGE temperature was 7ºC cooler than the present, ice sheets a mile thick were on top of Manhattan!
A good analogy of the difference between weather and climate is to consider a swimming pool. Imagine that the pool is being slowly filled. If someone dives in there will be waves. The waves are weather, and the average water level is the climate. A diver jumping into the pool the next day will create more waves, but the water level (aka the climate) will be higher as more water flows into the pool.
In the atmosphere the water hose is increasing greenhouse gases. They will cause the climate to warm but we will still have changing weather (waves). Climate scientists use models to forecast the average water level in the pool, not the waves. A good basic explanation of climate models is available in Climate Change- A Multidisciplinary Approach by William Burroughs.
Source: AMS Policy Statement on Weather Analysis and Forecasting. Bull. Amer Met. Soc., 79, 2161-2163
Basic rebuttal written by dansat
Update July 2015:
Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial
Last updated on 15 July 2015 by pattimer. View Archives
Kotchakorn
The scientists aren't trying to predict the weather in the future, they are trying to predict the cimate. What is the difference? Climate is the average of the weather, normally considered as the 30 year average. Weather is what happens day-to-day. Predicting the two is quite different. Let me use two examples to highlight this.
1. A man is walking his dog along the beach. The dog is on a lead. If we watch the dog it wanders up and down randomly, down to the waters edge, up to sniff some seaweed - quite random. But the man is walking in a straight line along the beach, and the dog's movement is limited by how long the lead is. Can we predict exactly where the dog will be when the man has walked further along the beach? No, that is like predicting the weather. But we can predict that if the man continues along his current course, the dog's position will be within a certain distance from the man.
The dog is weather, random, but a bounded randomness. The man and the length of the lead is climate. If the man continues on the same path, with the same lead, the climate hasn't changed. If the man moves higher up the beach, the dog has to go with him. The dog can now reach higher up the beach, but it can't reach as close to the water. When the man moves, the climate has changed.
2. Or consider a swimming pool. It has a certain amount of water in it. If nobody uses the pool for a long time its surface will be very smooth and level. It is easy to estimate how much water is in the pool.
But if people are using the pool the surface is very rough and unven. Each little wave and trough is like the weather, random. But if the amount of water in the pool doesn't change, then the waves are all within a certain height of each other. The waves on the top are the weather, how much water is inthe pool is climate. Predicting one if very different from predicting the other. And if we add more water to the pool, that is like changing the climate.