alaska's arctic tundra. and at the most northerly tip of the state, the town of barrow, much closer to the north pole than washington d.c. this is america's very on climate change brought line. with the summer melt under way, this is the last chance to drive over the sea ice without the risk of falling through. the results of years of field work show the ice is getting thinner and younker. it really it -- rarely lasts for more than three or four years. of arctic iceme has fallen by more than half in a generation. all this reflective surface that we see here is someone keeping the planet cooler. it will be gone. >> alaska significance in the climate story is about calls as well as effect. the north slope is america's biggest oil field. the u.s. is desperate to tap new sources of alaskan oil. 30we have safely drilled wells in the arctic in the 1980's. it can be done. i am confident it will be done. i am confident it will be done safely. >> another oil company in france has looked at the arctic and said the risks are too big, it still would do too much damage. >> the arctic is going to be developed. who do we want in t