Ireland has officially signed up to the Paris Agreement on climate change.
Representatives from countries around the world are signing the deal today at a special ceremony at the UN headquarters in New York.
More than 170 countries are lining up to sign the Paris Agreement on climate change as the landmark deal takes a key step towards coming into force years ahead of schedule.
The acting Minister for the Environment Alan Kelly is signed on behalf of Ireland.
States that do not sign on Friday have a year to do so.
"The era of consumption without consequences is over," UN secretary-general Ban Ki-moon told the gathering.
Many expect the climate agreement to come into force long before the original deadline of 2020. Some say it could happen this year.
After signing, countries must formally approve the Paris Agreement through their domestic procedures. The United Nations says 15 countries, several of them small island states under threat from rising seas, are set to do that on Friday by depositing their instruments of ratification.
The agreement will enter into force once 55 countries representing at least 55% of global emissions have formally joined it. The United States and China, which together account for nearly 40% of global emissions, have said they intend to join this year.
Maros Sefcovic, the energy chief for another top emitter, the 28-nation European Union, told reporters the EU wants to be in the "first wave" of ratifying countries.
French President Francois Hollande said he will ask parliament to ratify the Paris Agreement on climate change by this summer. "There is no turning back now," Mr Hollande told the gathering.
Countries that had not yet indicated they would sign the agreement on Friday include some of the world's largest oil producers, including Saudi Arabia, Iraq, Nigeria and Kazakhstan, the World Resources Institute said.
The Paris Agreement, the world's response to hotter temperatures, rising seas and other impacts of climate change, was reached in December as a major breakthrough in UN climate negotiations, which for years were slowed by disputes between rich and poor countries over who should do what.
Under the agreement, countries set their own targets for reducing emissions of carbon dioxide and other greenhouse gases. The targets are not legally binding, but countries must update them every five years.
Already, states face pressure to do more. Scientific analyses show the initial set of targets that countries pledged before Paris do not match the agreement's long-term goal to keep global warming below 2C, compared with pre-industrial times. Global average temperatures have already climbed by almost 1C. Last year was the hottest on record.
The latest analysis by the Climate Interactive research group shows the Paris pledges put the world on track for 3.5C of warming. A separate analysis by Climate Action Tracker, a European group, projected warming of 2.7C.
Either way, scientists say the consequences could be catastrophic in some places, wiping out crops, flooding coastal areas and melting Arctic sea ice.
The US is a key concern for the Paris Agreement as other countries worry what the next president might do. Analysts say that if the agreement enters into force before Barack Obama leaves office in January, it would be more complicated for his successor to withdraw from the deal, because it would take four years to do so under the agreement's rules.