Protesters to hold day of action at climate change summit in Copenhagen . U.N. chief : ` We are not going to let this happen again' Score: U.N. Secretary-General Ban Ki-moon told nations Tuesday that they had the chance to `` change the course of our history '' if they worked together to limit carbon emissions that are blamed for increasing global temperatures . World leaders begin arriving for `` high-level '' negotiations in final days of summit .
Protesters to hold day of action at climate change summit in Copenhagen . U.N. chief : ` We are not going to let this happen again' Score: World leaders begin arriving for `` high-level '' negotiations in final days of summit .