OPEC announced Friday it will reduce oil production by 1.5 million barrels a day because of the global slowdown of oil demand. This could drive gas prices back up, but that might not be such a bad thing.

The New York Times reported that the emergency meeting ended with the decision to reduce OPEC output by 5 percent, which is 2 percent of the overall global consumption of oil, starting Nov.1.

Oil prices are trading below $64 a barrel, down from $145 a barrel in July.

The U.S. is the world’s largest oil consumer, but demand in the U.S. for oil is down and the lowest in five years. Last month it fell to 18.6 million barrels a day according to the Department of Energy.

As of Monday, gas now averages $2.66 a gallon, down from $4.11 on July 17. OPEC seems desperate to keep gas prices up.

Although this might seem bad for the economy to raise gas prices, it might be the best thing for the environment and green energy movement. When gas prices were high Americans started limiting their gasoline consumption and went to more earth-friendly forms of transportation such as biking, carpooling, taking the bus, walking, or even planning their trips more efficiently. Hopefully the fall of gas prices won’t revert those who now think more about their gasoline consumption.   

If you're concerned about climate change, and want to reduce carbon emissions, you might be surprised how easy it is to figure out how much carbon dioxide is produced by, say, driving to work. Sure, there are a lot of carbon calculators out there where you can plug in all the numbers on how much you drive, and how much electricity you use. But it's also surprisingly easy to estimate yourself.

Here’s how you can do it. If you go to the EPA carbon calculator it gives you recognizable units, like gallons and pounds. (And slightly more confusing units like carbon dioxide equivalent.  Essentially, they’re adding the other greenhouse gases into the number for carbon dioxide. But there’s more about that on the calculator page.)

It’s very simple to use, so here are results I got from spending a few minutes with the EPA calculator and playing with the numbers.

* Every gallon of gas burned produces about 22 pounds of carbon dioxide equivalent. (So for simplicity, let's round down to 20.)
* Every therm of natural gas burned produces about 11 pounds. (I think it’s fair to round down to 10.)
* Every kilowatt hour (kWh) of electricity produces about 1.7 pounds.
(If rounding up to 2 seems too painful, consider where your electricity comes from. If it comes from coal, yep, round up to 2. For natural gas, you can figure 1 pound. There are some statistics that help justify those numbers here.)

So when you fill up your gas tank, you have a number in gallons. Take it times 20 and you're awfully close to knowing how much carbon dioxide burning that tank of gas will produce. Same thing goes for your electric bill. Take a look at the number of kilowatt hours. Double it (in most cases) and you’re looking at pounds of greenhouse gas emissions.

Want to think more about pounds of carbon emissions and how to lose them? Here are a few related articles:

Eight Projects for Instant Energy Savings, Mother Earth News 

On Carbon Calculators, Grist 

What Makes a Pound of Carbon Dioxide, The Green Guide