If it looks like a duck, walks like a duck, and squawks like a duck, it’s a duck.

This kernel of folk wisdom often comes to mind when I see or hear someone deny that the earth is warming and that we are contributing to this warming when we burn fossil fuels.  He or she is refusing to face obvious facts and the simple logic that connects them.

• Scientists have understood for over a century how CO2 in the atmosphere works to reduce the escape into space of radiant energy from the earth’s surface.  This mechanism is now called ”greenhouse warming” and CO2 is a “greenhouse gas”.  When more energy is retained, the average global temperature rises.
• Precise and reliable measurements show that the concentration of CO2 in the atmosphere is steadily rising as the result of human activity, primarily the burning of fossil fuels.
• Physical evidence of global warming is all around us.  From the Himalayas to the Andes glaciers are melting, as are the snows of Kilimanjaro.  Sea levels are rising from this meltwater and thermal expansion.  Summer sea ice is growing thinner in the Arctic and is expected to melt entirely.  Zones of hardiness in the northern hemisphere are moving northward.  Pine beetles, that in earlier years could not withstand the cold winters, are now destroying millions of acres of forest in the US and Canada.  Tropical diseases, like malaria and dengue fever, are moving north.

We understand the greenhouse warming mechanism and the role of CO2, we know that we are driving this mechanism by burning fossil fuel and adding CO2 to the atmosphere, and we know the earth is warming.  This is proof enough.

Reasonable people may disagree on the rate of this warming and how far it will go.  But the facts, that the earth is warming, we are contributing to the warming by burning fossil fuels, and we can reduce the burning and slow the warming, are beyond dispute.

Bill Allen,  August 3, 2010    <>    OFFby2050