This frozen ground often contains more water than normal soil, and the freezing of that water makes the ground more solid. If not, it would be too mushy to hold up a house.
During our journey through the Arctic this summer, we visited Herschel Island, where scientists gather every summer to study the impact of climate change. Dr Chris Burn, a geologist and permafrost expert from Canada's Carleton University, goes to Herschel every year to measure the loss of permafrost. He has seen a lot of change over the years.
'We know there has been a 2 degrees Celsius warming of the permafrost in the past century,' Burns said. 'This is happening because of higher air temperatures at the surface.'
A recent report by Canada's National Round Table on the Environment and the Economy pointed out that roads, houses and other structures will be under even more threat as climate change worsens. According to the report, Canada's Arctic dwellers are not prepared for what global warming will do to their homes and infrastructure. Along with sinking buildings, they face erosion of their coastlines.
'Melting permafrost is undermining building foundations and threatens roads, pipelines and communications infrastructure,' the report said. Airport runways could also become unusable due to the melting, scientists warn.
Often it's hard to remember why climate change is important. But when you are in the Arctic and the ground under your feet is sinking as it melts, climate change starts to make sense.
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