It doesn't take a rocket scientist (or an earth scientist for that matter) to know that today's weather isn't the weather we grew up with – and today's climate isn't the climate of yesterday. As a scientist who studies this topic daily, I and my colleagues know why. Human greenhouse gas emissions have led to a 40% increase in the amount of carbon dioxide in the atmosphere. As a result, the Earth is gaining energy at an alarming rate.

So what? How will all this energy change the climate (and the weather we experience)? Well some changes are pretty straightforward… First scientists expect that the Earth will globally get warmer, although the warming will happen much faster in some areas than others. We expect the rate of drying (and consequently drought) will increase in some areas while other regions will become wetter with more flooding. We expect to lose ice, see oceans rise, changes to the ocean acidity level, among other changes.

Some changes, however, have been harder to unearth but recent exciting findings are shining some illumination. Among the most exciting areas of research is the connection between loss of arctic sea ice and extreme weather in the Northern Hemisphere. The arctic, which has been warming at an alarming rate has seen an approximately 75% decrease in the summer sea ice volume. Consequently arctic waters, which had been covered by ice, are now absorbing tremendous amounts of solar energy during the summer and releasing it to the atmosphere during the autumn and early winter.

This change in the arctic energy balance has begun to have an effect on the weather patterns, particularly on the jet stream. This rapidly flowing stream of high-altitude air separates the cold dry arctic air from warmer moist air closer to the equator. When that jet stream dips southward, watch out! Cold air and potential downpours or snow storms may be coming your way. Recently, the jet stream has been more likely to be found in an undulating, slowly moving state.

Nasa image of meandering polar jet stream



What does this mean to us? It means that we shouldn't be surprised to see more severe weather that lasts for longer durations. Our weather can be expected to whiplash from one extreme to another.

In the U.S. we are seeing some evidence of this. Alternating wet, snowy winters and warm non-winters. Summers of either extreme heat and drought – or unbelievable flooding.

But don't just take my word for it. A leading researcher in this area, Dr. Jennifer Francis says,

The Arctic is warming two-to-three times faster than the rest of the northern hemisphere -- the loss of sea ice, spring snow cover, increased Greenland melting, and permafrost degradation are all symptoms of and contributors to this warming. It's inconceivable that a change of this scale and magnitude will not have substantial impacts on the atmosphere, ocean, and land both within the Arctic and also beyond the Arctic where millions of people live. These impacts will affect not only the physical system -- such as weather patterns and ocean circulation -- but also life on land and in the ocean. Exactly how these effects play out is a wide-open topic of research.

Jennifer Francis

Regarding the specific impact of global warming on Superstorm Sandy, her colleague, Dr. Charles Greene added,

Images of flooded subway stations in New York City, demolished towns on the New Jersey shore, and autumn blizzard conditions in Appalachia will be etched in the nation's psyche for quite some time. With the increasing frequency of extreme weather events serving as a backdrop, many people are asking what role, if any, did anthropogenic climate change play in the development of Superstorm Sandy? If one takes into account the record loss of Arctic sea ice this past September, then perhaps the likelihood of greenhouse warming playing a significant role in Sandy's evolution as an extra-tropical superstorm is at least as plausible as the idea that (she) was simply a freak of nature.

Charles Greene



If we are seeing this type of extreme weather already, it makes one wonder what the world will be like in 10, 20, or 50 years. We will certainly have to deal with many more costly weather disasters. More European heat waves like 2003 or 2010; more Midwest United States droughts of 2011 and 2012. Repeated 1000 year floods, larger storms like Sandy, and yes…. We will even see snow… lots of it. Charles Greene's November 2012 Scientific American paper was prescient – he virtually predicted the extreme weather, including Sandy and the series of nor'easters that have battered the Eastern Seaboard this past winter. It makes one wonder about other events. The alternating years of droughts and floods in the Midwest that have converted last year's severe dryout into today's severe floods in Indiana and Illinois? Are they tied to human emissions? What about the oscillating heat waves/drought and flooding episodes in Australia? We can only hope that this emerging science continues to advance so that these questions can be answered.

There are two takeaway messages to all of this. First, all of today's weather is now affected by climate change. Second, there is a tremendous cost to the extremes we are seeing. For those who say taking action to stop climate change is too expensive, we only have to point to the costs we are incurring right now. It is clear that it is too expensive to ignore this problem.

But don't just take it from me, ask my students. Engineering student Sara Backlund, who attends my heat transfer course recently remarked,

Last summer was crazy hot – so hot my soccer games had to be cut short. This spring it is incredibly cold – it's May and we haven't even started practicing and our games are being canceled. Even I can see the weather is changing…

So, it may not take a rocket scientist to tell us we're changing the weather… It might just take a bright engineering student.

• Dr. John Abraham of University of St. Thomas, the Climate Science Rapid Response Team and the Climate Science Legal Defense Fund