They aim to establish rules, figure out financing and build ways to verify that nations are meeting their commitments.
COP 21, in 2015, led to the landmark Paris Agreement.
The world is now on course to overshoot by far the limits for global warming agreed in the landmark 2015 Paris accord on climate change, which were meant to prevent more extreme weather, rising sea levels and the loss of plant and animal species.
Hosting the talks in the heart of its coal region of Silesia, Poland tried to set the tone for the two-week meeting by promoting the idea of a "just transition" for miners and other workers facing layoffs as countries adopt alternative energy sources.
The UN chief thanked Modi for his commitment to increase India's nationally determined contributions to the Paris Agreement.
"Even as we witness devastating climate impacts causing havoc across the world, we are still not doing enough, nor moving fast enough, to prevent irreversible and catastrophic climate disruption", Guterres told delegates from nearly 200 countries who gathered in the city of Katowice.
Climate change was an important topic on this year's agenda, which comes on the heels of an ominous climate report by the United Nations and the World Meteorological Organization's announcement that the average global temperature for 2018 will likely be the fourth highest on record, and 20 of the world's warmest years happened in the last 22 years.
"If we fail, the Arctic and Antarctic will continue to melt, corals will bleach and then die, the oceans will rise, more people will die from air pollution, water scarcity will plague a significant proportion of humanity, and the cost of disasters will skyrocket", he warned.
Calling Mr Trump "meshugge" - Yiddish for "crazy" - for deciding to withdraw from the Paris accord, Schwarzenegger insisted the climate deal had widespread support at local and state levels in the US.
President Donald Trump has threatened to pull the USA out of the Paris agreement because of what he says is the economic damage the treaty's provisions would cause.
Climate Action Minister Richard Bruton, who is in Poland for the talks, said he fully endorsed UN Secretary-General António Guterres's comments about the need to take action.
The UN negotiations got off to a chaotic start in the Polish mining city of Katowice Sunday, with the opening session delayed almost three hours by a series out last-ditch submissions from countries.
The US has previously pledged to cut its greenhouse gas emissions 26 to 28 percent below 2005 levels by 2025, and to provide billions in aid for poorer countries by 2020.
Host country Poland is proposing a slow approach to ease the financial blow from move away from fossil fuels.
German Ambassador in Dhaka Peter Fahrenholtz stressed that the negative effects of climate change becoming perceptible for more and more people worldwide must immediately be taken seriously and must urgently be fought on a global level.
"It also takes place in a scenario where we have clear signals about the urgency with which we need to address the issues of climate change".