Canada’s boreal forest soaks up 22% of the carbon stored on the earth’s land surface … Jasper National Park, Alberta, Canada. Photograph: Karen Schwartz/AP

In the far north latitudes, buried within a seemingly endless expanse of evergreen forests, the authorities in Canada are building up one of the world’s best natural defences against global warming.

In a series of initiatives, Canadian provincial governments and aboriginal leaders have set aside vast tracts of coniferous woods, wetlands, and peat. The conservation drive bans logging, mining, and oil drilling on some 250m acres – an area more than twice the size of California.

Barack Obama speaks during a visit to Florida Power & Light’s Desoto Next Generation Solar Energy Centre. Photo: Steve Nesius/AO

The epic confrontation about how America will power the economy of the future formally got underway today amid stark warnings from the Obama administration of the costs of inaction on energy reform.

Today’s hearing, the first of three blockbuster sessions in the Senate, marks a last heave by administration officials and Democratic leaders to advance a bill to reduce America’s greenhouse gas emissions before an international climate change meeting at Copenhagen, now just six weeks away.

One of the main water sources outside Moyale in Kenya runs dry. Photograph: Sarah Elliott/EPA

One of the world’s most influential scientists has warned that climate change could devastate Africa, predicting an increase in catastrophic food shortages.

Professor Sir Gordon Conway, the outgoing chief scientist at the UK’s Department for International Development, and former head of the philanthropic Rockefeller Foundation, argued in a new scientific paper (pdf) that the continent is already warming faster than the global average and that people living there can expect more intense droughts, floods and storm surges.