Good afternoon. My name is Scott Denning. I'm a Professor of Atmospheric Science 

at Colorado State University. I've published about 100 papers in the peer-reviewed 

climate literature. I'm a former Editor of the Journal of Climate, and I served for five 

years as founding Science Chair for the North American Carbon Program. 

I support the proposed rules because in my expert opinion they are a step in the 

right direction to avoid dangerous and extremely expensive damages to the United 

States. 

Climate Change is Simple, Serious, and Solvable. 

You may be surprised to hear from a climate scientist that climate change is 

simple, but I want to explain to you that our concern about greenhouse gas doesn't 

come from computer models. It doesn't come from recent temperatures. It's not 

rocket science! It's absolutely consistent with your everyday experience of the 

world. 

The Earth's climate results from the balance between the heat we receive from the 

Sun and the heat Earth radiates back to space. If more heat comes in than goes out, it 

warms up. If more heat goes out than comes in it cools off. 

Carbon dioxide gas absorbs outgoing heat because of the shape of its molecules. For 

every doubling of the number of heat-absorbing CO2molecules in the air, we hold 

on to 4 Watts of extra heat on every square meter of the planet. That's the 

equivalent of one 4-watt nightlight bulb on every square meter of the Earth, 24 

hours a day, 365 days a year, for centuries to come. Believe it or not, we've know 

this since before light bulbs were invented. The heat-absorbing properties of CO2 

gas were first measured over 150 years ago, in 1863, by John Tyndall. Since that 

time the measurements have gotten better and better, but the answer hasn't 

changed. 

We expect CO2to warm the climate for the same reason we expect day to be 

warmer than night, summer to be warmer than winter, and Miami to be warmer 

than Minneapolis. This doesn't come from computer models. It comes from 

measurements. We expect CO2to warm the climate because we know that when you 

add heat to things, they change their temperature! 

Climate change is serious. Warmer air evaporates more water than colder air. 

Here in the west we know how precious water is, and we can't afford to waste what 

little we have by having it evaporate from our farms and ranches and reservoirs. We 

get almost all of our water from mountain snowpacks, and our economy would 

suffer tremendously if we lost that snow. The strongest predictor of wildfire in the 

west is summer temperatures, and we've seen the acreage burned double in our 

region in 30 years, even with the small amount of warming we've had so far. 

Without major emissions cuts, western forests may burn so frequently they'll be 

completely replaced by grass and shrubs. In other parts of the US, the problem isn't 

too little water but too much. Sea level rise in a warming climate could destroy 
trillions of dollars worth of real estate along the coasts, though we certainly don't 

expect rising seas to reach the Mile High City! 

Climate change is solvable. We have the technologies already in hand to 

dramatically reduce emissions while strengthening our economy and creating jobs. 

A complete transformation of the global economy to non-fossil energy has been 

estimated to cost about 1% of global GDP. Our ancestors spent about that much 

retrofitting the world's cities with indoor plumbing a century ago, and it was so 

worth it! And that money wasn't gone - it created millions of jobs for plumbers and 

contractors and the grocers and farmers who fed them. 

Opponents of these rules claim the US is weak and that our people are incapable of 

meeting this challenge, of solving our climate problem. They will tell you that our 

feeble economy needs to be propped up by energy we dig from the ground. They are 

wrong. Our economy is the strongest in the world, because our people have always 

been willing to apply ingenuity and hard work to turn problems into opportunities. 

I urge you to implement the proposed rules, because I believe our children can be as 

creative and hard-working as our ancestors. 

Scott Denning, Ph.D. 

Monfort Professor of Atmospheric Science 

1371 Campus Delivery 

Fort Collins, CO 80523 

(970-491-8359