The countervailing effects don't cancel each other out. They're both signs of the changes we are bringing to the planet.
In the seas to our north, sea ice is melting at a perilous pace. This year crushed earlier records for the lowest sea-ice extent ever recorded in the Arctic. Some scientists predict that in four years, Arctic sea ice may collapse entirely during the summer months.
It turns out that the northern pole is not the only one setting records with unusual ice patterns. But to the south, the story is different: record-setting sea-ice extent. That is to say: While the ice to the north is melting away, the ice to the south is growing, extended over 19.44 million square kilometers this year, breaking the previous record (set in 2006) of 19.39 million square kilometers..
Now, lest you get all, "Phew. So glad this who global warming thing is being balanced out," let me tell you plainly: That is not how it works. These are not counteracting phenomena that somehow cancel each other out. Both of these sea-ice trends are the result of changes in our planet's climate, but the effects are different because our hemispheres work in different ways.
To begin to understand this, look north first. The ice there is melting for a pretty straightforward reason: It is getting warmer. As the sea ice melts, the dark oceans absorb more of the suns rays than the bright ice (which reflected them), and the process accelerates.