One often hears it said that those warning us about the dangers of global warming are 'alarmists', presenting only the 'worst case scenarios'. I believe that global warming is a serious issue that requires immediate action, but as a scientist I have to admit there are some alarmists out there making wild claims. When an issue has become as politically charged and muddied by ego as global warming has, I find it useful to take a step back and look at the numbers. Very often simple 'back of the envelope' calculations can do wonders in helping you sort through spin and hyperbole.

As a scientist defending your position, it is useful to start your argument by granting the opposing view every possible benefit of the doubt, within reason. That anthropogenic global warming is real is an established fact, no scientific organization denies this, and NO ONE seriously argues that global warming is not occurring, anthropogenic or not. So lets start with one claim that is often jumped on as being 'alarmist'- that global warming will lead to disastrous raising of sea level. (Please note, sea level rise is NOT what concerns the scientists the most, but is what the certainly alarmist media and entertainment industry love to latch onto).

Currently, estimates of temperature increase vary from 1.1 degrees C, to 6.4 degrees C by 2100. Let's assume a global temperature rise of 2 degrees Celsius- a number FIRMLY on the low side of the estimated range. Let's start with the 'Best case' scenario for sea level rise.
Let's start with the unrealistic assumption that a 2 degree rise would NOT result in ANY melting of ice caps (remember, we start by making assumptions that greatly favor the opposing point of view).

(The following calculations are NOT rigorous, they are ONLY to illustrate that anyone can easily check that the numbers given by scientists using complicated data and computer simulations are NOT unreasonable)
If we assume a temperature rise of 2 degrees and NO ice melt there will still be (by simple physics) an increase of sea level due to thermal expansion of the existing sea water.
It is a simple enough matter to calculate a rough back of the envelope estimate for the sea level rise from thermal expansion; all you need are the following numbers:
Estimated volume of Earth's oceans: VOceans= 1.3*109km3
Estimated surface area of Earth's oceans: AOceans= 3.61*108km2
Coefficient of volumetric thermal expansion: Beta=1.6*10-5K-1

Now, in the interest of scientific accuracy and honesty let me state that my value of Beta is, by far, the greatest uncertain factor in this calculation. The mean temperature of the earth's ocean is estimated to be ~3.5 degrees Celsius, Beta varies nonlinearly around this temperature, it is approximately 0 at 4 degrees, and increases rapidly with temperature. I chose a value of Beta for water at 5 degrees Celsius. Those wishing to attack my calculation could, correctly, point to this choice of Beta as being the weakest point in my argument. You are welcome to do so, but as we will see my numbers end up being in line with far more detailed calculations. I initially did the calculation for Beta at twenty degrees and got a MUCH larger value, I probably could have gotten away with giving that larger number, but that would be engaging in the same non-scientific nonsense as those claiming that global warming is hype.

The increase in ocean volume from a 2 degree rise neglecting ice melt is given by:

Delta VOceans= Beta*VOceans= 2*(1.6*10-5)*(1.3*109km3)=4.16*104km3
To estimate the rise in sea level, H, that this equates to I use Delta VOceans=H*AOceans and solve for H. This gives: H=1.15*10-4km, or~11.5cm

11.5 cm, or 4.5 inches.

Doesn't seem like much, what could 4.5 inches do?

OK, it will be a real problem for coral reef ecosystems, some inhabited islands will get smaller- maybe uninhabitable (since for every inch rise in the ocean you will lose far many more inches of land), coastal cities will have to adapt at some cost, areas already prone to storm surge flooding may become too prone to keep living in, we will lose a lot of our wetlands, coastal infrastructure will have to be modified... it will be costly, but manageable- tougher on the third world than for us, but that’s their problem.

It will be costly, but manageable. :) Heck, I can hear some here giggling now that we will just build a 6" high wall around the USA- no big deal...

Problem is, this is the VERY unrealistic best case. Not only have we left out Ice melt, but we haven’t even mentioned other issues like agriculture, fresh water supply, eco-system collapse, altered ocean currents (and the climate changes that will cause), displaced populations and the conflicts that will arise...

Let's just go a small step further, let's look at a little ice melt- surely we can ALL agree there would be some ice melt, right? In fact we have hard data showing its already occurring.

Let's start small; lets just consider the Greenland ice sheet (this may not seem like starting small, but it is- the Antarctic ice sheet has 10 times more ice, but we will assume it magically remains untouched by global warming).

The Greenland ice sheet has about 2.6 million cubic kilometers of ice. (for comparison, the Antarctic land mass has about 25 million cubic kilometers of ice on it). 2.6 million cubic kilometers of ice is ~2.34 million cubic kilometers of water, if all of the Greenland ice sheet were to melt (I AM NOT SUGGESTING THAT THIS WILL HAPPEN IN THE NEXT CENTURY AND NEITHER IS THE IPCC!! ANYONE SAYING THAT IT WILL ALL MELT IN THE NEAR FUTURE YOU ARE FREE TO CALL AN ALARMIST!) IF all that water were added to the ocean it would raise sea level by (simple calc using numbers off the web) :

Delta VOceans=2.34*106km3=H*AOceans; H=6.4 m or ~21feet

most online values say 7.2 meters. Close enough for this crude calculation. Only a SMALL fraction of this ice needs to melt in order to give the possible result of 59 cm sea rise that the conservative IPCC report states. And the calculation above only considers a SMALL fraction of the available ice. There are numerous indications that the rate of ice melt is significantly higher than the rate assumed in the IIPC.

IT IS CLEAR that the IIPC numbers are NOT alarmist.

A rise of half a meter would lead to great die-offs of coral reefs (as would the simple change in temperature), a huge wipe out of coastal wetlands, increased flooding, devastation of ecosystems. The predicted temperature change, and precipitation patterns, would be a massive trauma for agriculture in the developed world, and a disaster for the developing world. Precipitation changes predicted include increased flooding and increased drought (NOT a contradictory prediction). The loss of fresh water supply from glaciers and snowmelt would put large populations at risk. Coastal cities would have to engineer for the increase or suffer the consequences.

I will add more on why I believe there is a conclusive reason to act on anthropogenic global warming.

IF you choose to reply to this:
1) Do not respond with pithy, wise-ass 1-liners.
2) Do not respond with random cut and paste from a blog, dont cut and paste a random paragraph of Ayn Rand and act like you have made your point.
3) Respond with arguments that you can back up, or don’t respond it all. Keep the rest of the crap on flame, there is a thread for it…
4) I have intentionally left openings for those wishing to throw in the party line as their argument, do so at your own risk- if you want to debate me on this you better make sure your claims are based in fact.
-Arrell