Climate change is undeniable, irreversible and caused by human activity, and governments can only reduce its dire effects on global communities by cutting greenhouse gas emissions over the coming decades, a UN report released Sunday said. The UN's panel on climate change (IPCC) said in the report that unavoidable consequences of rising temperatures include longer and more frequent heat waves, more extreme precipitation events, an increasingly acidic ocean and rising global sea levels. Those effects can be mitigated, the report showed, but it will require governments to slash emissions to near zero levels by the end of the century, dpa reported.