Over the last two years, evidence has accumulated that the IPCC reports released just two years ago underestimate the pace of climate change. Nature provides this summary. See also this article in Science Daily; and there are plenty more like it;
Emissions from fossil fuels growing faster than any of the scenarios included in the IPCC reports (news article ; original paper here). And recent studies indicate the effects are irreversible., at least for the next 1000 years.
Arctic Sea Ice, which is probably the most obvious “canary in the coal mine” is melting faster than the models predicted, and will likely never recover (Story from IPY here);
Greenland and Antarctic ice sheets melting 100 years ahead of schedule (news report; original papers here and here). Meanwhile new studies show the effect on the coastlines will be worse than previously thought, especially in North America and around the Indian Ocean (press release here; original paper here).
Sea level rise following the worst case scenario given in the IPCC reports (news report; original paper here and here).
Oceans soaking up less CO2, and hence losing their role as a carbon sink. (news report; original paper here)
And finally some emerging evidence of massive methane releases as the permafrost melts (news report; no peer-reviewed paper yet).
I think there’s a typo in your title: you have an extra question mark, and the ‘is’ ought to go between the the words “Climate Change” and “Accelerating”. 😉
The recommendations from the scientists at the Scientific Congress in Copenhagen are worth a read. They say clearly that “there is a significant risk that many of the trends will accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts.”:
http://climatecongress.ku.dk/newsroom/congress_key_messages/