Showing posts from September, 2010

The global impact of ocean cooling in the 1960s

A common complaint made by so-called climate sceptics is the fact that global temperatures haven’t precisely tracked the trend of rising greenhouse gas levels over the twentieth century . The argument seems to be that if carbon dioxide emissions are a significant driver of climate change then temperatures should have inexorably risen over the recent past. The assumption behind all this is that natural processes don’t have any major effect on hemispheric or global temperatures. Recent published work shows this just isn’t the case. When we look at data collected by weather stations since the nineteenth century, we find the world’s temperature has increased by around 0.8 °C . This may not sound much but the average for the planet hides a complex mix of regional warming and cooling in different places over different times. The sceptics have picked up on the fact that in spite of the long-term trend, there hasn’t been a constant upward drift. The early increase in temperature up to th

A lesson from past global warming

When looking to the future, it’s only natural to scrutinise yesterday. Be it studying the form of a favoured racehorse, probing twentieth century economic trade figures or analyzing international diplomatic relations over the centuries, history offers an insight into what might lie ahead. But written records aren’t our only source of information when we wish to learn from the past. Geology can serve a similar purpose when looking at climate change. Although the timescale may seem interminably long, records of our planet’s environment, preserved within rock, mud and ice (often referred to as ‘natural archives’ within scientific journals), can extend historical testimony and provide unique insights into the climate of our planet and where things might be heading in times to come. The question is how? To look at one example from the past, let’s ignore virtually all of the 4.5 billion years of our planet’s history and concentrate on only the most recent sliver of time.  Over the last