Scientists say that soil across a huge part of the continent, including western Ethiopia, is producing the gas because of drought and changing land use.
His speech at Sydney’s Conservative Political Action Conference has been leaked to newspapers.
The veteran BBC presenter said overweight people could stop the country being overpopulated if they die a decade earlier than the rest of the population.
Shadow chancellor John McDonnell said: "We would not block something like that. We would let the Scottish people decide. That’s democracy."
A study has found marine ecosystems are suffering them frequently putting plant and animal life at risk - and the people who depend on them
Current reform proposals of the EU Commission on the Common Agricultural Policy (CAP) are "unlikely" to improve environmental protection, say scientists
Rising temperatures are expected to cause massive loss of ice in the Arctic.
NASA’s Transiting Exoplanet Survey Satellite (TESS), a mission designed to comb the heavens for exoplanets, has discovered its first potentially habitable world outside of our own solar system
Digitising historic weather data has extended the records back to 1884, bringing in new coldest years but the warmest years are all recent.