Flying's impact on the environment

According to British airways flying makes a 1.6% impact today on global warming out of all human activities... I wonder if the UN's IPCC study agrees with this stat.?

From BA's site >>>

"Aviation and the environment

Although the worldwide contribution of flying on global warming is relatively small (1.6% according to last year’s government commissioned Stern report), it is forecast to grow to 5% by 2050. Despite the fact that road transport produces six times more greenhouse gas emissions and power generation produces 16 times more, we are determined to tackle this important issue as an airline and as a business."