What is the difference between weather and climate change and how do we differentiate the two?

Weather is short term events that can be be anything from temperature during a specific hour, daily max/min temps, a day of clear skies, or a week long cold snap. You are right though that climate is closely connected to weather. Climate is the culmination of many weather events for a period of time. You can’t neatly define weather as a 24 hours period or climate as needing to be a 30 years or more. It’s fairly relative, and that’s how both sides can confuse and misuse the terms when it comes to regular people talking about it. The people who actually work within the science have a firm understanding of the difference, but that often gets distorted when their results are translated to the public either by their own misunderstandings on the topic, or by intentional manipulation by someone with an agenda.

Because climate is basically the summed and average effect of many weather events, a single weather event can be used as evidence towards the climate trend. That doesn’t mean a single weather event defines the climate though. Instead, you add that one point to many others where each point influences the outcome of determining the climate. There is no clear distinction between short term data and long term. It’s simply data. When you and track it for a week, or even a year, it’s still short term in the topic of climate and weather. However, many of those short term observations combined then become long term observations which then can be used to describe the general climate rather than just the weather for a day or year.

When people mention that the weather is X out today and that proves/ disproves global warming, they are incorrect. Proponents (and opponents) that are familiar with the science to not make that mistake. Usually it’s only news anchors, talk show hosts, etc. without much background that make those comments. Instead the weather on that day is supporting evidence towards determining the climate. Does a hotter than normal day support climate warming? Yes, but that one day is only one small piece of the climate picture. You need to look at many of those pieces to gain a clearer picture of the actual climate. Then that is only the climate for the one area you looked at. At that point you need to consider we’re looking at global warming. In some areas the climate may actually get colder, but overall, most areas would be warming. It’s the average temperature of all these areas combined that is increasing under global warming.

You do highlight a major issue in the topic though. The science is sound, but people easily get confused, or don’t take the time to learn the terminology and the truth gets muddled by the media and word of mouth unless you’re actually in a circle of people with scientific understanding specifically about climate. Many posts you see from non-scientists whether it’s an opponent or proponent are pretty evident of this misunderstanding. Usually that comes from only scratching the surface of understanding the topic rather than investigating it.

As a rough rule of thumb a climate is determined by taking the mean weather conditions over a period of 30 years or more. Many climate records are updated on a monthly basis and as such, last month’s weather will now be incorporated into the climatic record, this means that the current climate is determined by both very recent weather and historic weather as well and is therefore dynamic and constantly changing. For arguments sake let’s say that December was an unusually cold month, when the December data are incorporated into the climatic record the effect will be to reduce the overall average global temperature. But, because there will be at least 359 other months worth of data, the effect is going to be very small indeed. If it were that climates were determined by just ten years worth of data then the difference that a single month could have would be multiplied three-fold. In determining whether the climate is changing we need to compare recent conditions with a static baseline from history. Different baselines are used but generally they’re either 1951 to 1980 or 1961 to 1990. If there’s a difference between the current climate and the baseline then we can determine that the climate is changing. What we deem to be the current climate is constantly changing, if we’re going to determine if the climate is indeed changing we need to use fixed reference points and so monthly or annual means over a 30 or more year period will be used, from this it will be established if there are any discernible trends. In this respect, a generic definition of climate is going to give you something that is continually being revised but for analytical or statistical purposes it’s something that is represented by a series of numbers. Even something over such a long time-scale as the Milankovitch cycle influences are always going to affect the weather first. Then as the weather becomes incorporated into the climatic data, the cyclical influence becomes more apparent in the climate record. The same is true for the short term cycles and one-off events.

Climate is "The general or average weather conditions of a certain region, including temperature, rainfall, and wind. On Earth, climate is most affected by latitude, the tilt of the Earth's axis, the movements of the Earth's wind belts, the difference in temperatures of land and sea, and topography. Human activity, especially relating to actions relating to the depletion of the ozone layer, is also an important factor.

I would also also point out the huge impact that ocean currents and phenomena have upon the global weather patterns. I do not believe 30, or even 50, year cycles qualify as climate for we are talking about longterm conditions. If we only use the last 30 years as a norm for comparison are we not rigging the entire comparative process? Values must continue to reflect historical data for as far back as we reliably have it.

I am a proponent that we will soon be moving into a 30-50 year cooling phase in our overall climatic cycle. I prefer to wait and see as opposed to throwing out wild assumptions that we are quickly approaching a "tipping point" in global warming. Besides which, this alleged tipping point could just as easily trigger another ice age as create global deserts.

I disagree to some extent with the answers provided so far.

Like you, I struggle with the term "climate change".

Many have said weather is what happens in 24 hours... I disagree.

For the sake of the argument, I will base my understanding on where I live, in Australia, in a temperate zone.

We have 4 distinct seasons.

The WEATHER in each season is predictable.

Spring is mild, Summer is hot. Winter is cold, Autumn(Fall) is mild.

So I say the weather in Summer is hot...for a period of 3 months, not 24 hours.

Certainly, some days are hotter than others.

A fraction of a degree in temperature rise has made no discernible difference to the weather.

The climate has not changed.

If we start getting snow in Summer and heatwaves in Winter, then yes we have climate change.

There are actually three terms that mean different things: Weather, Regional Climate, and Global Climate.

Weather is what is happening right now in one place.

Regional Climate is the expected frequency of weather events in one place.

Global Climate is based on the total heat energy being retained by the whole system.

In the discussion of global climate change, the important difference is that weather involves heat moving from one place to another. Global Climate is the total temperature of the entire system. People commonly express, in innocent ignorance, that the global environment cannot possibly be warming because it is so cold right here today. We these people don't understand is that weather moves: it did not "get cold" where you live, cold air moved down from the arctic and the warmer air moved someplace else. Looking at weather, you do not get the big picture. Globally, the temperatures of the air and ocean surface (but not deep ocean) are taken and tracked every day. Even when we have rapid warming, we still have freezing cold someplace. People look at their weather for the past two years and see cold winters in their small corner of the world, but are not aware that winter temperaturs parts of the arctic tundra have warmed by 6 degrees.

No climate scientist points to any weather event as proof of global climate change. Even during events such as the Russian heat wave, scientists are careful to say that having such extreme events is normal -- they will become (or have become) more common but it will take a number of years to see it.

Imagine you have a set of dice that you believe are loaded so that snake-eyes come up one out of every 12 rolls (rather than 1/36 as normal). You can roll the dice and get a 7 -- that does not prove that the dice are normal. You roll again and get snake-eyes, that's one snake-eyes in two rolls which is highly unsusual and fits the theory but does not prove anything. You need a lot of date. If you roll 100 times and get 8 snake-eyes then you believe more confidently that you have loaded dice but you still have not proved it and you cannot say that anyone of those 8 times was "caused" by the dice being loaded -- they might have come up snake-eyes anyhow. But after 500 throws, if you got snake-eyes 40 times and you know normal dice would average 13 times, you know know beyond a reasonable doubt that the dice are loaded -- but you still cannot claim that the loading "caused" any single one of the snake-eyes. It is all "probability" which is more easily understood by people who have taken statistics in school.

Simply put, weather is what happens day by day, and climate change is the pattern of weather changes over the long term. Note this is not the pattern of weather but of the change in weather. If You averaged 8 storms a year before and 10 storms a year after, then what you can say is that there's been a 25% increase in storms because of... You can't ascribe any particular storm to climate change, but you can attribute the 25% increase in number of storms to climate change.

I have seen people argue that particular increase means you can ascribe 20% of each storm to global warming. I understand what they're saying, and I agree basically with the idea, but I'm not sure it makes physical sense to say 20% of a storm is from global warming and 80% is normal weather. It sure fits the math, though.

The last bit is the intensity of our hypothetical storm. Let's say "before", the hurricane average intensity for the season is Cat 3, and "after" the average is Cat 4. Then it's pretty clear that climate change has caused a 1 category increase in the intensity of storms. Now I agree this may also match up with a decrease in the total storms. Let's go back to 8 storms before, and only 6 after, since this is one likely scenario. Then, with hurricanes, you've got climate change reducing the number of storms by 25% while kicking the strength up 1 category. (And how do you point to the 2 particular storms that did NOT happen?)

Let me state here that I in no way intend anyone to believe these numbers I just made up. I was using them for examples, and keeping the calculations easy. And to finish up, I actually don't see outrageous statements by proponents. What I really see is the claim by skeptics that we say that, when all I've seen proponents say is more or less what I've said above.

Now to the tax item. Pigouvian taxes (a unit tax on each item ) cannot necessarily make the industry producing the taxed product maximally efficient. The argument presented in the paper referenced discusses optimal efficiency vs social costs. But the model does not account for catastrophic social costs. It acts as if a social cost can be mitigated by a payment. This is not always the case. Take real-life examples of social policies that led to war. What's the economics of that? Economic theory works well on paper, and in ideal or near-ideal conditions, but it does not account for all that can happen. Rather, it generally ignores catastrophes. "Externalities" is a very bland word for hurricanes, floods, droughts...

Finally, you are using a somewhat out-of-touch bit of economics to say do nothing about AGW, as far as I can see. Why, when we already know many of the consequences, and have started experiencing them, do you say we should make no provisions for change? If this isn't your tax argument, please clarify it. (And what does politics have to do with science, anyway? They are very different things.)

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EDIT: Hello, Red, you're welcome. Heh, been sitting here 10 minutes after typing the previous sentence, trying to figure just how to go on. Clearly this splits into 2 parts, one science and one politics/philosophy. While the science is important, it can slide into the background for a while, after a quick question on just how strong you think the middle-of-the-road future climate projections are, and which way they would be off. But further science discussion can wait for another time.

My worry is that the question comes down to what sort of approaches are workable vs what sorts of approaches are effective. I will concede the initial point to you - Pigouvian taxes are almost never able to properly balance production efficiently; it is only in very rare instances that everything balances perfectly and you get maximum production efficiency for minimal social cost. At least that's what I got from a quick go-through of my reference. My economics courses were 4 decades ago, so I googled and read/skimmed the math. So my approach will be naive.

While this single tax, applied on each item, can't fully balance things, the paper indicates that, for some instances, Pigouvian taxes can come close to doing what they are meant. This means they can be pretty effective, no? While we can't do it all with cap and trade, for example, we can get say halfway, which certainly mitigates the worst effects, and try other things to finish solving the problem. Thus, we can look to past instances of cap and trade for guidance. My answer's far too long to include 1990 Clean Air Act & consequences, but it works pretty well. Certainly a lot better than liming the thousands of lakes in the Adirondacks, which was our best answer to acid rain before cap and trade.

But a piecemeal approach to the consequences while ignoring the source won't work.How many hundreds of thousands of miles/kilometers have to be diked to protect lowland areas from rising seas?

I will say that both sides do in fact use these concepts interchangeably to boost their own arguments. They also use terms that are sort of in between like "lowest Arctic sea ice extent", "warmest decade on record", "highest rainfall on record", "extended drought", early spring, etc.

The problem is the words "on record". This usually means since 1850 or so when temperature records began somewhat more accurately. Of course, the climate was cooler back then since we had just come out of the Little Ice Age.

If we went back on very long geological time frames like millions of years, then we would have no records to speak of the last 150 years. The Earth has been much hotter, much colder, been covered with ice and been free of ice.

So you can be pretty sure that when someone mentions the weather today, yesterday or last year or mentions some sort of "record", they are just trying to juice up their argument.

You are correct that no individual weather event should be used as proof of AGW or as evidence against it. AGW is a statement about long-term (decades to centuries) change to the global mean temperature, and if there happens to be record cold temperatures in Punxsutawney on a particular day it is pretty much insignificant to the global mean over a long period. However the rising trend in global temperatures should mean that noise about the trend (the "weather") will have more excursions above the climatological mean than below. What that means is that it becomes much more likely that all-time high temperatures will be set than all-time low temperatures, so if we look at large numbers of those it DOES tell us something about whether AGW is true or not, and in fact the number of extreme warm events has been exceeding the number of extreme cold events for a long time now. That is documented in the IPCC report. It's not quite fair though to blame that all on AGW, because urban heat islands have made it less likely for new minimum temperatures to be set. Nevertheless there does seem to be a clear signal of warming in the extreme events (but not in any particular event).

Some "weather" events take place over longer time periods, such as drought, which may be years in the making. Since those type things sample longer time periods there is a better chance that they are showing us long-term trends. Still, we have to be careful making that interpretation because those things certainly happened before AGW also.

EDIT: Wow, six thumbs down from the deniers so far, for an answer that not even Roy Spencer would disagree with. Do any of you that gave me thumbs down even care whether or not an answer is right or wrong?

as you said weather is a period of 24 hours whereas climate change is a period of 30 years (or more)

unfortunetely, even though the weather is going quite wrong, i don't THINK that it can be classified as climate as after all it's far from the 30 years that define climate