Recent research revealed Auckland's mean temperature was rising, rainfall patterns were changing and the coastlines were being affected by the rising sea level.
The effects of climate change were expected to get more serious over time, according to the research.
The council was also committed to making sure the temperature did not rise more than 1.5C.
Auckland mayor Phil Goff said action needed to be taken urgently to ensure future generations would not inherit a world devastated by global heating.
"Scientists tell us that if we don't take action, the effects of heating will be environmentally and economically catastrophic.
"In declaring an emergency, we are signalling the urgency of action needed to mitigate and adapt to the impact of rising world temperatures and extreme weather events."
As part of its commitment to reducing climate change, the council would continue to make climate change a key part of its programmes and decisions. This included putting climate change impact statements on all council committee reports.
It would also continue to advocate for greater central government leadership and lead examples in monitoring and reducing the council's greenhouse gas emissions.