Climate predictions

[tolbiny]

Ten years ago when I was interested in climate and ecology in high school it was just plain accepted that long range forecasting was out of our reach. The complexity of weather patterns, not fully understanding how variables interact (or even if all the most important variables were known) gave my teachers an aura of confidence when describing how little we knew about the weather.

What has so fundementally changed? I routinely hear about predictions of the the long term climate effects of global warming with little or no mention of caveats about these difficulties in predictions. Have the past ten years of satellites, ice cores and computer modeling taught us enough to be confident in these predictions (confident enough to encourage action to change the path)? I really have no understanding of how to treat these predictions from a probabilistic view or a scientific accuracy view.

I guess the question is, how well can we fordcast the next 30 years?

[ApeAttack]

I'm a graduate student at UC Irvine and have read a lot of papers and heard a lot of lectures on the issue of global climate change (GCC).

Scientists DO recognize that there is still great uncertainty in the extent global climate change (GCC) will occur over the next century. If you read the IPCC report, different models can vary significantly in their predictions of the average temperature increase in the future and this uncertainty increases as they look further in time. The uncertainty is due to different assumptions used in the models. For example, there is still a HUGE uncertainty in the effect aerosols (not those from hairspray cans) play in GCC.

However, the models all predict the same general trends: there will be a rise in the average global temperature, the arctic will get hotter, etc. This is in part because greenhouse gases (GHGs) such as CO2, CH4, N2O, etc... have relatively well-defined chemistry and absorption spectra (although there is still uncertainty in the emission budgets of GHGs). The radiative forcing from GHGs play a huge role in the radiative forcing budget of earth.

Scientists now have more confidence in predicting that GCC will occur because,
1) Computers have become a lot faster, allowing for models to include more data.
2) The science has become better (the input data has become more accurate).
3) More data has been gathered over the last decade that shows GCC is beginning to occur.

In short, scientists DO recognize there is still great uncertainty in the precision of model predictions, but there is little uncertainty in the idea that there is a general trend toward an increase in the average global temperature.

Here are links from the 2001 IPCC report.

Avg global temp. increase

Other graphics from the IPCC report

CO2 concentrations - current + predictions

[Woolygimp]

I hear Global Warming advocates cite information saying the temperature is the highest it's been in 400,000 years.

Then I heard skeptics saying, the temperature is following a natural 1,500 year pattern and the temperature is well within normal means.

These are dealing with facts, events that have already happened and this isn't theorycrafting. They can't both be right...

[ApeAttack]

[ QUOTE ]
I hear Global Warming advocates cite information saying the temperature is the highest it's been in 400,000 years.

Then I heard skeptics saying, the temperature is following a natural 1,500 year pattern and the temperature is well within normal means.

These are dealing with facts, events that have already happened and this isn't theorycrafting. They can't both be right...

[/ QUOTE ]


Two points...
1) I think that most scientists who advocate GCC is occuring will say that man's role is only part of the story. Non-anthropogenic (man-made) sources of GCC are influencing the earth's climate as well. However, keep in mind that it only takes a few degree increase in the average global temperatures to make massive changes in the climate. Almost every numerical model predicts that a few degree increase is a very strong possibility in the next decade if emissions are left unchecked.

2) The world's TOP scientists in the field are almost unanamous in their belief that humans are significantly impacting earth's climate. This includes almost every noble prize winner as well. The question is how severely will man impact the climate in the future. These 'skeptics' you speak of most likes either (a) don't understand the basic physics and chemistry behind GCC and/or (b) have political motives.


I must once again state that among the top scientists in the field (people who have spent their entire academic careers studying this topic), almost every one believes that man's contribution to GCC is occuring and will get more severe if left unchecked. Their beliefs are based on fundamental principles of chemistry and physics, not political.

[Silent A]

[ QUOTE ]
Ten years ago when I was interested in climate and ecology in high school it was just plain accepted that long range forecasting was out of our reach. The complexity of weather patterns, not fully understanding how variables interact (or even if all the most important variables were known) gave my teachers an aura of confidence when describing how little we knew about the weather.

What has so fundementally changed? I routinely hear about predictions of the the long term climate effects of global warming with little or no mention of caveats about these difficulties in predictions. Have the past ten years of satellites, ice cores and computer modeling taught us enough to be confident in these predictions (confident enough to encourage action to change the path)? I really have no understanding of how to treat these predictions from a probabilistic view or a scientific accuracy view.

I guess the question is, how well can we fordcast the next 30 years?

[/ QUOTE ]

First lesson you need to learn:

Climate and weather are not the same thing.

Weather means specific conditions at a particular point at a particular time. It is inherently impossible to predict accurately, especially more than a week or so into the future.

Climate refers to average conitions, over several decades, of a relatively large area on a monthly, seasonal, or annual basis. It's still hard to predict, but it's not inherently impossible.

[surftheiop]

"I must once again state that among the top scientists in the field (people who have spent their entire academic careers studying this topic), almost every one believes "that man's contribution to GCC is occuring and will get more severe if left unchecked. Their beliefs are based on fundamental principles of chemistry and physics, not political."

Even if not political wouldnt you say these top scientists would have huge economic incentives (ie. sell books, get governments to fund their research, have jobs,etc) to make global warming seem urgent?

[latefordinner]

No, I think that selling out to XOM and other companies to be a paid shill for the no such thing as global warming crowd would be much more lucrative.

[Rearden]

[ QUOTE ]
Even if not political wouldnt you say these top scientists would have huge economic incentives (ie. sell books, get governments to fund their research, have jobs,etc) to make global warming seem urgent?

[/ QUOTE ]

Compared to the myriad of other fields of scientific research... no. I think most serious statements on global warming suggest that the damage has been done and is being done. I have no idea what direct economic impact would go to particular science groups in the sense that any acclaim would cast doubt. Your statement is phrased as if to say the more noise a certain idea or policy gets the more we should ignore it; thats not how mainstream scientific consensus is formed. If however youre looking for examples of "science" motivated by money and belief and not actual data "The Republican War on Science" is your book (rest assured though it also attacks insane "science" claims on the left as well)

I would state that global warming is urgent. Simply because it still snowed in most of the US this year and because most weather patterns were normal does not discount documented long term trends that when properly applied to form theories of future system behavior... it all looks pretty bleak and damn serious. If it was just (somehow) an issue of minor global temperature increase... ok. But its not nearly as isolated. Imagine the impact of global climate change on everything from malaria and west nile virus spreads to changing currents and populations in global fisheries or weather patterns changing to damage regional crop yeilds, etc. Geology shows us that the world was at times decidedly unfriendly toward life...maybe the future is just as negative.

I believe fully that based on the data avaliable today that the world climate will be altered dramatically in the next 25 years resulting in different weather patterns (more severe storms, droughts in previously moderate areas, also farming in greenland as a minor plus) and shifts in natural systems (currents, insects, etc) and that such alterations if they occur will negatively impact human beings as a species..... I do still hope that I am somehow wrong in this

[latefordinner]

also I am so tired of hearing conservative talk radio show hosts talk about snow storms as evidence against global warming - it shows a complete lack of understanding of what the global warming phenomenon is all about (I have long contended that the phrase should be "catastrophic climate change")

"global warming" isn't about a slightly longer growing season in canada and needing to turn on the AC a little earlier in Florida, it's about massive and irreversible shifts in habitats (precipitation changes, weather patterns, sea levels, sea pH, etc) that could lead to the collapse of large ecosystems

[ApeAttack]

Even if not political wouldnt you say these top scientists would have huge economic incentives (ie. sell books, get governments to fund their research, have jobs,etc) to make global warming seem urgent?

[/ QUOTE ]


At the university, I am surrounded by professors and researchers who will never publish a book. Only a small fraction of scientists will ever publish anything more than journal articles (and they don't directly get money for that).

It is true that many scientists must write research proposals to get funding and this could bias the proposals toward studying topics that are more accepted among the scientific community. However, this is generally not the case. These people genuinely want to do a good job. Researchers put their reputation on the line every time they publish something in an peer-reviewed journal. If they turn out to be wrong later, they stand to lose a lot of respect (which could lead to loss of funding, etc.). In general, researchers are very conservative in making large claims. In my classes, professors sometimes joke about ridiculous claims made by some lone scientists in the past.

The idea that humans are playing a significant role in GCC did not suddenly popup overnight. It has been evolving slowly over the decades. During this time, many scientific papers have been published in peer-reviewed journals (not an easy thing to do, trust me), evidence has been gathered, and many different researchers have come to the same conclusion regarding this issue.

The reason for the urgency is because the planet's atmosphere takes a long time to recover and the rate of greenhouse gas output is rising at a ridiculous rate. It took a long time for the ozone layer to even begin recovering from CFC emissions (although it still has a long way to go).