By Gordon Brown
The views expressed are his own.

Next week's 2011 G20 meeting has the power to write a new chapter in the response to the economic downturn. But every day, as nations announce currency controls, capital controls, new tariffs and other protectionist measures, the G2O’s room for maneuver is being significantly narrowed. Already the cumulative impact of a wave of mercantilist measures is threatening to turn decades of globalization into reverse, returning us to the economic history of the 1930s, and condemning at least the western parts of the world to a decade of low growth and high unemployment.