GLOBAL WARMING has already begun to affect Britain in many small ways, from swallows arriving early to reduced gas use in winter, the Government announced yesterday.

Warmer springs mean swallows are now arriving on average six days earlier than in the 1970s, and oak trees are coming into leaf 19 days earlier than in the 1950s, according to a report. And warmer winters mean that noticeably less gas is being used in households in the late months of the year, while the proportion of deaths from all causes occurring in January has dropped.

These and other changes are in a database of climate change indicators for Britain, created jointly by the Institute of Terrestrial Ecology and the University of East Anglia, which the Government unveiled yesterday. It was previewed by The Independent earlier this year. The 34 indicators are designed to pick up the impact of global warming on society and the economy as well as on the natural world. They include factors as diverse as the number of insurance claims for subsidence and storm damage, the number of holidays taken in the UK and the amount of skiing in Scotland, as well as the number of vineyards in the UK and the dates at which wild birds are laying their eggs. They also include direct climate data, such as the record of air temperature in central England, which dates back to 1659, the longest such series of data in the world.

Four of the five warmest years in the whole record have occurred in the last decade - 1989, 1990, 1995 and 1997. Mike Hulme, of the University of East Anglia, disclosed that the last two winters (97-98 and 98-99), taken together, were the least cold for 350 years, with only one "cold day" - defined as when the average temperature in central England drops below zero and stays there - between them. The indicators are provisional but those monitored so far provided "firm evidence" that the climate was not only changing, but already affecting our environment and our society, the Environment minister, Michael Meacher, said yesterday.