How can climate change predictions over past centuries be reliable when 7 day weather forecasting is tricky?

Question

How can climate change predictions over past centuries be reliable when 7 day weather forecasting is tricky?

Answer 1

The results of past climate changes are already left behind for us to see. It's already happened.The future is just prediction,which is a different ball-game altogether.

Answer 2

Let's not talk about climate change in particular for a moment, but the larger (better?) question asked here, which I think is ...

If data collected over the last seven days is so variable that we don't know what is happening tomorrow, how can we possibly trust a whole bunch of this apparently unreliable data?

The answer is that general trends can become apparent, even when spcific data varies a lot.

Imagine that you wanted to lose weight, so you got on scale every single hour.   Your weight would jump up and down a lot.  Have a cup of coffee, weight jumps up.  Sweat a lot, weight goes down.   By the end of two days, you would have no idea what weight you really were, nevermind what weight you'd be the next time you stepped on the scale.   Now assume that you had six months of this hourly data, and were trying to determine if you had really lost weight.   Of course you could.  You'd draw a huge, average type line through all the data.  Some data would be below the line, some above.  But the trend would either be up or down.

Humans are natural pattern recognizers, but we typically want to spot the patterns that affect our immediate lives - seasonal cycles, high tide versus low tide, when the moon will be bright enough to hunt by.  Or even that when Joe gets his paycheck, he'll treat everyone to a round a bar.   And when we get a whole lot of data that jumps around a lot, we still try to find patterns in it.    "This time, the ace of hearts will turn up as the SECOND card.   I've noticed the pattern."  

It's much much more difficult for us to recognize or acknowledge patterns that happen on a scale much longer than our lives, or much shorter than our attention spans.   And we sometime casually attribute patterns to trends that aren't there.

But if we have a whole lot of good data, and we can look at it objectively and scientifically, we can draw "big picture" conclusions from data that seem to be random, or determine that data is random even when it seems to indicate a pattern.

I would strongly recommending doing a web search on simple statistics.  I think  you might find it interesting.  Unless I've misunderstood your question, in which case I apologize.

Good luck!

Answer 3

My thought exactly.   Can't believe everyone.

Answer 4

I agree that the climate predictions are not very reliable, but climate is easier to predict than the daily weather, so they are more reliable than the 7 day forecast I think.

Answer 5

hidden agenda,my friend.its a ploy to get us to jump on some bandwagon and leave our old lifestyles behind.not sure what it is but i do know the earth has been in constant change since day one and always will be.how can they really be convinced that us wee little humans can alter the path of something as massive as the earth.hogwash i tell ya!we will simply migrate or die,the same way all warm blooded creatures have done in the past.they shoulda thought before they taught us in schools.history and science.open up an old text book and just check on it.me?im moving to the desert,it will be a lush garden soon.

Answer 6

For the same reason you can't predict where the ball will fall on the next spin of roulette, but you can predict that over the long haul the house will win more than it loses.

Short term predictions are much more difficult than long-term predictions.

Answer 7

Climate change, what a ball of toffee.  It seems to me to be more of a conspiracy to cover up for the fact we're burning up oil faster than we can find it!  but what better way to get people to save energy than scaring them sh1tle55 with tales of doom and gloom!

The Earth has gone through ice-age then melt-down, followed by another ice-age, and so-on, but no-one ever says this is what is going to happen, the best you get is, "MAY" happen, "COULD" happen, or, "THE TREND SEEMS TO INDICATE" etc. etc.

There are so many variables, and such a fine line to draw, that if they're of by just a tiny fraction of a percent, the answers are in error, and computers don't have the ability to ask, "is this going wrong" they just churn out a glorified version of the error that was input by a human operator! and no matter how much we think we know about the way the Earth works, the Earth always has ways of proving how wrong we are.

35 years ago, scientists would have us believe that we were heading for a new ice-age, but it soon fizzled out.  The whole global warming cult was born of one Dutch scientists words being twisted into statement of fact, instead of the postulation that the world could be toppled into a global warm-up, by human activity.

In fifty years time, when they're tired of waiting, there will be a new "religion" for the doom and gloom merchants.  

Have you noticed that we've recently stopped calling it "global warming"?  It's now called "climate change" - what a political title?  It can go either way (warming or cooling) and they can still say they were right!  Either that, or they're as convinced as they once were!  Trouble is, once you get a big train rolling, it's very hard to back-pedal and stop it from running over you!!!

I for one, wouldn't mind being around to see egg on some smart-ar5e faces!!!!

Answer 8

They can't.  True believers are so welded to the belief that the world is warming, that they see this as their reality.

No one can predict what the temperatures will be in the future.  Any guess that is made is just a guess, no better then a coin toss.

Predicting the future is for mystics and soothsayers.  Not science.

Answer 9

For the same reason that you can't predict if you'll win a given bet or come out ahead/behind after a given day gambling in a casino, but you know that if you gamble long enough in casinos, you can safely predict you'll lose money.

Climate is the long-term average of weather.  Weather is unpredictable, but the unpredictability smoothes out over long periods of time.

As you can see in this plot, there is a lot of year-to-year variation in the global temperature, but the trend is consistently upward.

http://data.giss.nasa.gov/gistemp/graphs...

Answer 10

In science long term behavior is often predictable when short term data is very variable or "noisy".  Radioactivity is the classic example.  It's impossible to say when an individual atom of Lead -210 will decay, but nothing is more certain, than in 22.6 years half of them will.

Climate is like that.  Individual years may be warm or cool, but the overall trend today is VERY predictable.  See this graph:

http://data.giss.nasa.gov/gistemp/2007/

Answer 11

Because they deal with long term trends, not short term specifics.

Here's a parallel situation most people are familiar with that illustrates how this works.  Lets say you have a very good baseball team--and halfway through the season they are #1 with a  good lead over ohter  teams.  Now--you can predict--and with a VERY high degree of reliablity--that that team will be in the race for the championship come September--if they haven't already locked it up.

Bu--will they win tomorrow's game?  Yu can predict they will--but you'll be wrong 40% of the time.  You can predict the overalll trend: this is a god team--so they are going to win a  lot of games. But you CAN'T accurately predict the outcome of any single game.

Its the same principle with global warming--it is a long term trend, and MUCH more predictable than who will be in the pennant race. But predicting the next few days weather is an iffy affair.

Answer 12

The first step in preparing a WEATHER forecast is to collect a vast amount of information (data). This is collected from the earth's surface using instruments e.g. barometers, thermometers, anemometers and rain gauges as well as visual observations (e.g. cloud and weather type) from both manned and unmanned weather stations. At sea around 3,500 ships also collect information on a daily basis.

Data is collected from the atmosphere from launching balloons twice a day all around the world. These weather balloons record data such as temperature, pressure, humidity, and wind speed at different heights in the atmosphere.

Satellites are also used see how the atmosphere is behaving. The use of Doppler radar means its possible to see how rain or snow is acting in a cloud and how it might change. A Global Telecommunication System (GTS) has been set up to transfer just weather observations and forecasts around the world to different forecasting organisations.

This data is input into very powerful computers programmed to analyse it.

A typical weather forecasting model divides the globe into a grid of around 60 sq miles and then divides these squares vertically through 19 levels of the atmosphere. These computers process almost two million pieces of data every 10 minutes.

The results are then marked onto weather maps. Meteorologists read the weather maps, and by interpreting the data that appears on them, they are able to make a forecast. Local knowledge and experience also plays a part. Because the weather changes day-to-day, current weather forecasts are reliable for roughly only six to ten days, but a sudden change of wind direction can blow rain a few miles of course making an entirely accurate forecast difficult. Because there are so many local variables on a micro level it is difficult to be 100% accurate, and the further ahead the forecast is for the greater the margin for statistical slippage.

We know enough from trends to recognise when a region’s CLIMATE zone is changing.  For example tropical savannahs are a transitional stage between an arid climate and those of a tropical rainforest. If a savannah receives less and less rainfall then it begins to take on the characteristics of an arid area. When its rainfall, over a period of years, matches the amount found in an arid area then the vegetation and landscape will also begin to match those already found in an arid area. If it receives more rainfall than usual over a period of years then vegetation from neighbouring rainforest will take the opportunity to expand and colonise the grassland, which is now able to support forest.

In other words predicting climate is predicting the probability of events over time. We also have a historical record to compare events with. In many ways because climate change is forecast over a longer time-scale it is easier to predict trends and factor in periodic climatic events events such as El Ninos/La Ninas etc.

Given we can detect changes to climate we then have to look at the likely causes to try and determine how long and severe they will be, and at how any changes will effect other climate mechanisms and what the impacts of those will be.

We can tell from the TRENDS what the likely impacts will be and attempt to plan for them; in areas likely to suffer from increased drought for example.

The use of modern supercomputers to forecast climate change gives us a reasonably good look at the future. They’re tested by running them for the climate of the past five hundred years and comparing them against the known historical record. If they prove accurate doing that then they’re reasonably accurate forecasting the next few decades.