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A Journey to a New Land

Caribou
Multimedia Library

Dr. John Clague

Department of Earth Sciences, Simon Fraser University

Impact of Global Warming

The trend we have seen in the last century is one of warming. We know that globally and in North America climate has warmed - not a huge amount, but it has warmed about a degree in the last hundred years. Since the Little Ice Age ended, the climate has warmed by that amount. That has had a huge impact on glaciers. As I say, glaciers are very sensitive to even modest changes in climate and that amount of warming has driven glaciers back. It has driven alpine glaciers back. In some situations, glaciers have lost 50% or more of their mass just as a result of that modest warming over the last hundred years. And there have been instances where some glaciers have just disappeared completely. I mentioned Mount Kilimanjaro – the snows of Kilimanjaro are actually glaciers at the crest of Kilimanjaro and at present rates those glaciers are going to be completely gone in another twenty years if the climate continues to warm as it is. Glacier National Park in Montana – it’s called Glacier National Park because it supports glaciers. Well, a lot of those glaciers are disappearing and have disappeared, and again if this warming trend continues they will be lost as well.

Now this doesn’t mean that all glaciers on earth are going to disappear - some are more sensitive. The small ones, the ones that are kind of clinging to existence are the ones that are disappearing right now. But all through the world, geologists have documented this retreat in response to a modest amount of warming. The predictions that the atmospheric scientists make is that this warming is going to continue and maybe accelerate, and that we could be looking at average global temperatures several degrees warmer than they are today by the middle or end of this century. It remains to be seen, but it seems like the trend is going to continue, so we are going to continue to see this retraction of glaciers. They are going to increasingly melt. We’ve also documented some shrinkage on the Greenland ice sheet. This is even more of a concern because this is a large body of frozen water and if that becomes unhealthy and begins to retreat, you begin to have an impact on sea level. What you are doing when glaciers retreat is you are transferring that melted ice back to the sea and it causes the seas to rise. We know today from measurements of the sea surface that the sea is rising – a tiny, tiny amount just a couple of millimeters per year, and you might say, well, what’s the big deal? Well, if you extrapolate that over a significant period of time then it becomes more than just a tiny amount, it becomes a significant amount.

Sea level rise is a concern in low-lying areas. There are many countries around the world that are at sea level, such as Bangladesh. A significant portion of the land mass in Bangladesh is within a meter or two of sea level. So when you talk about even raising sea level a modest amount, you begin to dislocate people, you begin to introduce all sorts of problems. So a possible consequence of this warming that we are going to experience and the shrinkage of glaciers is an impact on humans through sea level rise. It’s a big concern. And it’s even a concern in North America and Europe, because when you think about it all the development that we have put in place on our coasts has been done with the assumption that sea level doesn’t change, other than the daily ebb and flow of tides. But all that development would be affected if the sea surface were to be higher than it is today. Even a meter or so, you have wharfs, you have docks, and you have people building beach front houses. If you raise sea level even a meter, you begin to have consequences for all that infrastructure. So even in a developed country where presumably you can take measures to deal with the problem, you have a big economic consequence to that. So what seemingly is kind of an academic subject actually has some very important social and political and economic implications as well.

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