From Mr Peter Schwartz.

Sir, Martin Wolf’s otherwise excellent column did not go far enough forward in time (“Prepare for a new era of oil shocks”, Comment, March 28). The current run-up in price is mainly political with diminished oil reaching the market from Libya, Iraq, Iran, Syria, Sudan and Yemen. As that oil comes back into the market it will be added to major new oil production from the US, Canada, Norway, Africa, Latin America and even Russia.

The previous peak of prices has led to a major expansion of new production from many sources: deep offshore, far north, oil sands and more. The result will be another price collapse within a few years, perhaps even this autumn.

This is just one more commodity price cycle of high prices driving new supplies and weak demand, followed by excess supply, falling prices and a return of demand growth driving prices back up. We have been through this five times in the last 40 years with little apparent learning. The big problem is that this will both confuse energy policy and, especially, make climate change policy much harder.

Peter Schwartz, Salesforce.com, San Francisco, CA, US

Former head of scenario planning at Royal Dutch Shell