Everyone has been exposed to the debate surrounding global warming. A lot of the scary consequences of global warming are found by the way of global climate models. It can be hard to decipher, at least from general reporting, as to where these models come from, how they are calculated, and how accurate they are. The following should clear up some of this mysterious witchcraft known as climate modeling and give scientific background to the problem.

Let’s first look at the scary facts. The world is warming. We have sufficient information to prove this fact. This is actually quite normal and it has been established that the Earth goes through warming and cooling periods. We were actually just in what some call a “little ice age” and would be expecting the temperature to warm up. The scary thing is how fast the world is warming. Most experts will say that the world has never warmed as fast as it is now. We do only have real data for the last 100 years or so, but with proxy data taken from ice cores we can infer the temperatures of the Earth up to 1,000 years in the past. However, note that this is still a relatively small period of time compared to the 4.5 billion years the Earth has been around. Below is data of temperature for the last 1,000 years. Please note that the grey is area is a margin of error.

You can see from the graph that the Earth, from the data that’s been collected, has never been directly observed to be so warm and the temperature has never been observed to rise so fast. Most will say that this data proves that the emission of greenhouse gases are the cause of the rapid warming of the Earth, but there is not consensus on this matter. If you look at the data for the CO₂ emissions for the past 1,000 years you see a correlation between the two graphs: The more CO₂, the hotter it is. This is a correlation, and not necessarily a causitive relationship, and therefore not conclusive evidence, but should not be taken lightly either.

So now we have some data, but how do we know the world is going to continue this trend? We have to look at the climate models. The model actually starts out quite simply. It’s just balancing a pretty simple equation. Sun heats earth at close to a constant H≈335 W/m². Earth radiates thermally following the Stefan-Boltzmann law (approximated as a perfect blackbody). The equation is as follows:

Where s is the Stefan-Boltzmann constant and T_e is the temperature of the Earth.

Simple enough equation, but fortunately this is not all that is going on. If you solve this equation for the temperature of the Earth we would be living on an earth with the average temperature at 277 K or 4˚C. If you factor in the albedo, which accounts for the amount of sunlight reflected back into space from clouds, ice, etc. you get the following equation.

Where A is the albedo and is approximately 0.3. When you solve this equation, the world turns out to be a frigid, frigid environment at -19˚C. This where greenhouse gases are our friends. From here our model gets quite a bit more complicated. About 20% of the thermal radiation from Earth passes through the atmosphere without being absorbed by greenhouse gases. The absorbed energy by greenhouse gases heats up the atmosphere. This sets up a two equation, two unknown problem. This equation is set up by doing an energy balance at the atmospheric level as well as the ground level of Earth.

Where T_a is the average atmospheric temperature. The radiation emission from the atmosphere is cut in half because it is radiating back to Earth and out into space.

If you solve for this model you get the temperature of the Earth to be about 15˚C. This is quite close to our observation of the global average temperature.

As the temperatures heat up this simple model will change. The Earth will be hotter, which means that it will evaporate more water. Water vapor is actually the largest constituent in the greenhouse gas effect, trapping nearly 70% of the thermal radiation attributed to the greenhouse effect. This may seem like a very bad thing, an endless increase in temperature, but water vapor also creates cloud cover. This will reflect a good portion of the sun’s radiation back into space. While this is an oversimplified model, it still shows that there is a balance. Now we just need to make it more accurate.

I will briefly explain how the modeling is actually done, how they know it’s at least somewhat accurate, and some problems with models. First let’s see how it’s done. You basically follow the equations above, but there are more variables present for the more accurate models. Some good models take into account boxes 1 deg latitude by one degree longitude. They take the temperature average for this box and calculate the balancing equation for about 30 different elavations. These calculations also include wind, water vapor, clouds, etc. You take all these variables into account and spread these boxes throughout the entire earth. That’s 360 longitude x 180 latitude x 30 heights x approximately 20 variables and you get about 40 million calculations. This is just for one time period. To model the future you have to do calculations every 20 minutes for 100 years. Enter supercomputers. Exit pretty pictures.

Above is the 4th Assessment Report (4th AR) from the Intergovernmental Panel on Climate Change (IPCC) showing the increase in temperature over the next 100 years for different regions. This information was just released and is available through IPCC.

One of the largest inaccuracies in the models is how much CO₂ there will be in the environment in the next year, 10 years, 100 years. This is mostly dependent on political and social stipulations. Since it is unknown what will happen economists have jumped on board and given the best and worst case scenarios for the next 100 years of CO₂ concentration in the atmosphere. Below is an image depicting the descrepency.

The graph shows different economists stances on the emissions of CO₂ in gigatons per year for the next 100 years. These are used in different models as shown on the right.

This creates quite a range in the proposed temperatures 100 years in the future. It also shows that no matter how people react to the problem the Earth will still warm. The most conservative model, the one with the least amount of CO₂ emissions, still raises the temperature of the Earth almost 2˚C. The most egregious model warms the Earth by 4˚C. These models show that human activities could double the amount of warming over the next 100 years. Below is a graph showing the temperatures for the CO₂ models in the graph above for the next 100 years. The two graphs are linked by their colors. The most conservative being green and the most egregious being dotted red.

While human activities are a major problem, this is not the only problem holding these super-meteorologists back. There is also a problem with scale. A one degree latitude and longitude box is quite a large area and there can only be one temperature, wind, water vapor, reflective properties value for each box. There are some efforts to shrink these boxes, therefore collecting more accurate data, but this requires a lot of computing power.

Another large problem is clouds. The very tall clouds (cumulonimbus) are very hard to model because they have ice, snow, rain and a combination of the three happening at different heights of the cloud—each form of water has different thermal and reflective properties. There is currently a JPL project to better understand what is happening in these clouds: CloudSat. The satellites’ instruments measure reflectivity and precipitation at different levels throughout these clouds by using radar. Climatologists are very excited about the data that is returning from CloudSat. With this data it will be easier to model how these clouds act, therefore creating more accurate models.

It is quite evident that global warming is occuring. It is also evident that human activities play a role in the warming of the Earth. This is where the science ends and the article ends. I will leave the human action, or lack of it up for debate.

The graphs used in this report can be found from the IPCC website. Some were also borrowed from Dr. Waliser, a JPL climatologist, who presented a talk at JPL on the subject.

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Written by Dunphy on 2006-09-28 01:25:53 Yay!!! Beaches in Canada!!!

Written by on 2006-09-28 06:54:34

Written by on 2006-09-28 06:54:38

Global Warming obviously! Written by Redders an Jono on 2006-09-28 07:44:06 We is guna uv da brill warn world wick boyakasha man i wear knucklebusters yay

you guys suck Written by bob marley on 2006-09-29 10:46:59

i hate you people Written by Bob Marley on 2006-09-29 10:48:36 You freakin scientists are really making me angry. Y

Yes Written by Doug on 2006-09-29 14:31:37 UK Enviro Minister: Fears climate change    http://news.bbc.co.uk/1/hi/uk_politics/5384206.stm    UK Environment Secretary David Miliband said he had thought he had been well-informed about climate change but had quickly been shocked by what he had learned since taking on the job. Five months into his job, Secretary David Miliband told the conference the science was more alarming than he had initially realised and that the dangers were far more immediate than he thought.  "We should be quite scared - I'm more scared than I was five months ago but I'm also more hopeful." He said the technology to produce carbon-free fuel was now in place and had to be rolled out on a "mass scale".   "People say there should be a debate about global warming. But I tell you the debate is over; the reckoning has begun. The truth is staring us in the face. Climate change is here, in our country; it is an issue for our generation as well as future generations; and those who deny it are the flat-earthers of the 21st century," he said.  BRITAIN risks "sleepwalking towards catastrophe" on climate change, the Environment claimed yesterday.

Written by Erin on 2006-09-30 04:15:59 what is with these comments?   do these people want to die? or maybe they just want their children to die... oh i don't know.. maybe they just like the smell of cow shit in the morning i don't know but i think you are the best, you homeless scientist =)

Written by Chris on 2006-10-04 10:30:05 The main graph in question has been contracticted. You might find usefull information here.  http://www.climatechangeissues.com/files/PDF/conf05mckitrick.pdf

Written by on 2006-10-04 17:01:06

eat my world Written by witchhunter on 2006-10-09 17:03:09 Ya all arrrr goinn ta hell ho ho ho

here ye my fing world go Written by dig my dirt on 2006-10-09 17:06:39 By e by e crasy fing world

Great Read Written by DHippy on 2006-10-18 09:57:41 I think this article is one of the easiest to understand while still being richly scientific with regard to global warming issues. Great stuff.

Program manager Written by yaakov on 2007-02-07 08:12:07 The same information used for your 1000 year review is available to show a 3000 year span; however, the results will show a non supportive basis for the effect of human responsiblity. Thus the end of government funding and control.

Guru Written by Mr TT on 2007-02-23 17:27:15 An interesting article. First time I've seen an politically neutral argument on this whole issue. Only question I have is how do they know that CO2 is what is causing GW? Seems to me they jump past the correlation thing right to proof.  I am still looking for that evidence, to be convinced that this thing is our fault.

people will believe anything in writing Written by Julie on 2007-03-18 16:33:15 this article makes no sense! how can you show a graph, not even explain what its variables mean, and say 'this proves my point'? idiots.

Written by on 2007-04-23 02:24:10

Written by on 2007-04-23 02:34:01

Written by on 2007-05-18 09:56:24 im at school an very bored and have to do a project in global warming you should make it easier for a 14-5 can understand

Kid in school Written by Dave on 2007-06-03 08:22:14 Hey there kid in school who has to do a project on global warming! Do a report showing global warming is a hoax! That will really piss off your stupid liberal teacher!

tinkerer Written by John Wayne on 2007-06-08 15:42:29 So how do we know the earth isnt just warming up, they keep finding people and animals in the ice thats melting so I would guess that ice hasnt been there forever.

Global warming Written by chey on 2007-09-11 19:31:52 If all people would come together and stop the fighting amoungst us, we could all work on a solution to this problem.

Written by on 2007-09-25 01:43:08

CDR Written by Navcdr on 2007-10-15 17:00:21   What is in dispute is whether global warming is man made. This webpage pretty much proves it to be true.  I have seen the same graph a half dozen times.   I think this is the most conclusive proof that indeed global warming is caused by Co2 emmisions which come from autos and coal fired power plants.  The last 50 plus years shows the line going way off the charts.  Only coal fired power plants and the heavy increase of fossil fuel have been around the last 50 years to make Co2's happen to this level.   In times past .. a spike in the graph was only caused by things like a volcano eruption.

Written by on 2007-10-23 10:37:16 h r there are glaicers coming all we all r going to die because there is going to be no land to live on due to icebergs

Written by on 2007-10-23 10:38:38 you guys are a hunk of junk you believe in the dumbest crap ever so u can suck my hairy

Written by on 2007-10-23 10:41:18 holy cow

Written by on 2007-10-23 10:41:23 stacies mom got it going on and world is going to freeze

Written by on 2007-10-23 10:42:23 t and g, u guys suck and shutup

Written by on 2007-10-23 10:43:50 tis a hoax gobal warming is not realy because the ice bergs are growing in alaska they have grown .4 million square miles... so the earth is cooling not warming dip ships!!

Written by on 2007-10-23 10:43:50 tis a hoax gobal warming is not realy because the ice bergs are growing in alaska they have grown .4 million square miles... so the earth is cooling not warming dip ships!!

Written by on 2007-10-23 10:48:43 yeah like 4500 years ago we where taking temp. reading so they don't know wht they are talking about.

Written by on 2007-10-23 10:49:39 this is the biggest hoax ever..when was our kin folk taking temps.. way back when the temp. devices were not around

global warming Written by lyric on 2007-11-05 11:01:24 what is it why is it such a big thing whats the worry

Written by loser on 2007-11-18 09:49:27 it is our fault!!!!!!!

still laughin Written by laughin at your own contradict on 2008-01-12 19:22:25 I came here hoping to see some real proof and found only opinion.....Statistics are not proof..they are just opinion...and you know about those?     You say yourself that you are only looking at a small window of the past....1k years is not even a statistically sound sampling of 5 billion years....

5 billion years? Written by on 2008-01-21 19:02:14 The book i read (bible) doesn't accept the fact that the earth has been around for 5 billion years.    being the republican i am, i will take your 'facts' (read as opinion) and substitute it with my fantasy world which is closer to reality than the crap you're smoking. i'm with G.W. Bush on this one, there is no issue with Global Warming, its false hood to make people think that 'going green' will help the world.

Written by kayla on 2008-01-27 16:31:07 its sad people actually dont care about issues that matter,. ica caps melting, droughts, extinct animals... its so sad..

yayo Written by jippie on 2008-02-06 02:28:58 wiiieeee

Written by jnkl; on 2008-02-25 15:11:08

yo Written by amy colio on 2008-02-28 10:26:02 blahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

Cree Prophecy Written by Foster on 2008-03-10 18:15:43 “When all the trees have been cut down, when all the animals have been hunted, when all the waters are polluted, when all the air is unsafe to breathe, only then will you discover you cannot eat money.”- Cree Prophecy

global warming (bad) Written by alissa on 2008-04-09 09:41:26 if we keep doing what we are doing to this planet. the planet will die out. that is very bad.

Written by on 2008-04-25 23:53:25

Written by Brad on 2008-05-20 17:18:09 "If we keep doing what we are doing to this planet. the planet will die out. that is very bad."     True, but it has more to do with clearing forests, polluting fresh water sources and depleting non-renewable sources than it does with global warming. It's very hard to prove whether or not it exists (which is what our "leaders" count on) but I believe it's just another global scare tactic like terrorism. Anyone can "prove" anything with statistics because statistics can be created to fit any argument. This article proves nothing.

Written by on 2008-05-26 17:03:55 i like turtles

Written by j on 2008-05-27 20:17:23

Don't be ignorant... Written by LogicStick on 2008-07-11 13:15:30 Any self respecting scientist would read this article...    http://www.junkscience.com/Greenhouse/

Rodolfo Written by Kelby on 2008-07-21 23:43:12 3a2bb405e2357b96aab7d408867c1d95   http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95   http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95   [url]http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95[url]

Rodolfo Written by Kelby on 2008-07-21 23:43:15 3a2bb405e2357b96aab7d408867c1d95   http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95   http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95   [url]http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95[url]

Rodolfo Written by Kelby on 2008-07-21 23:43:21 3a2bb405e2357b96aab7d408867c1d95   http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95   http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95   [url]http://njdokj.info/6efb1d7529869d8c6505820273703f80/3a2bb405e2357b96aab7d408867c1d95[url]

it's true Written by Monika on 2008-08-02 07:40:53 Everything about global warming is true, we are all going to die.

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