us amounts 
of methane. Methane gas is frozen and stored in the tundra, and when it 
is released, methane gas itself is a global-climated gas. It is four 
times worse than CO<INF>2</INF>. So when you melt the tundra, you 
accelerate the rate of change. Just like when you melt the ice, you 
accelerate the rate of warming.
  And that is why the North has warmed up so much, because the ice has 
melted and now the light is absorbed by the dark land rather than 
reflected back into space. It is called the feedba