Times (UK): When a New York oil trader pressed the button to buy a consignment of oil for $100 a barrel last week, he confirmed that we have entered a new era. As British householders are finding out to their cost, the days of cheap energy, responsible for so much modern-day prosperity, are over. If warnings about global warming did not make us change our behaviour, high prices might. The shift we are seeing, however, goes beyond household budgets and setting the thermostat lower. The world is …