North America bakes, while Northern Europe soaks

With another North American heatwave baking the region, people are once more questioning whether the weather is down to climate change or natural variation. Unfortunately it is one of the most difficult questions to answer categorically and often leaves the layman feeling confused or misinformed.

Steve Vavrus of the University of Wisconsin-Madison says "This is always the million-dollar question, but unfortunately, there's no definitive way to answer it. We've experienced extreme heat, drought, floods, wildfires and windstorms throughout history, so in a sense this is nothing unusual. We need time to assess whether this year's set of extreme weather events falls outside of normal variations."

The region has experienced more than its fair share of heatwaves and drought in recent years. Last winter was the fourth warmest on record, whilst spring was the warmest. "I think it's a harbinger of what's to come under greenhouse warming," says Vavrus. "Virtually all climate models simulate more intense and frequent heat waves as the climate warms, and most of the world has experienced increases in extreme heat during the past several decades."

Whilst the US is experiencing intense heat, Northern Europe is experiencing some of the wettest weather on record. In the UK, June was the coolest since 1991 and it was the equal wettest June (tied with 1860) on record. The blame has been placed on the jet stream, which is circulating much further south than normal, causing low pressure systems to dominate the British Isles and parts of northern Europe.

It has also been argued however, that the poor summer can be put down to climate change. Global averaged temperatures are still on the rise, and one near certainty of increasing global temperatures is more extremes. Whilst some seasons will break records in terms of heatwaves, others in localised regions can experience droughts or flooding events. And as has been seen in the UK, rainfall is likely to be more intense, creating more flood events.

The US drought however, continues a theme that has run through the last few decades. The temperature and lack of rainfall in the region in recent times has caused considerable problems for the region, yet average rainfall has actually increased in this time. Unfortunately, many of the wet regions tend to get wetter and receive more intense rainfall, whilst drier regions get drier.

It is of course endlessly debateable as to whether these weather events are connected with climate change. The confidence that comes with predicting long term climate comes with the process of averaging the results of many run throughs of models, which makes specific events almost impossible to attribute. What we can say, is that climate change is causing at least some of the problems we are seeing today, and if not creating these events, is most certainly exacerbating them.