Mr Bush, who has made surprisingly positive comments about carbon sequestration and fuel cells, could silence the critics by following suit.

ECONOMIST: The environment

They've made the allegation, certainly, both to the New York Times and in paperwork provided, that the carbon isotope test was positive, but they don't provide the documents that show that.

NPR: Landis Facing Uphill Battle on Doping Charges

We believe that the Long Carbon Americas and Europe division will continue to be the most valuable division for ArcelorMittal, primarily because of the positive outlook for the price of long carbon steel in the years to come.

FORBES: ArcelorMittal Stock Good For 10% Upside

"Anything that reduces food miles and other carbon emissions linked to food production is normally a positive thing, " said Dr Nicola Canon, lecturer in crop sciences at the UK's Royal Agricultural College.

CNN: Farm in the city could be supermarket of the future

Rather than abandon the theory, scientists fell back on the notion that the data jibed with the possibility that rising carbon dioxide levels were reinforcing the warming trend in what's called a positive feedback loop.

WSJ: Matt Ridley on Confirmation Bias and Global Warming | Mind & Matter

The finding fits with evidence from seven other countries that have had similar carbon tax shifts in place for over a decade, resulting in neutral or slightly positive effects on GDP.

FORBES: While U.S. Ponders Carbon Tax, In British Columbia It Appears To Be Working

Furthermore, there is a positive environmental impact as natural gas from shale, for example, produces roughly 50% of the carbon dioxide emissions compared to coal for the same energy output.

FORBES: Time for Solutions

So far, Whelan has received positive feedback from gym members who have used the equipment, and with the help of an interactive carbon calculator people can measure how much energy they are generating from their workout.

CNN: Virtuous cycles