A major United Nations climate change summit has begun in Poland, as tens of thousands also took to the streets in Brussels to demand urgent action.Nearly 200 nations are involved in the event, designed to build on the landmark 2015 Paris climate accord which set a goal of limiting climate change to well below 2C (3.6F).Image:Tens of thousands turned out in the Belgian capitalOfficials will thrash out a "rulebook" for declaring and monitoring cuts in greenhouse gases.They will also spell out how contributions will be made to a fund intended to mitigate the effects of climate change in less developed countries.Poland still gets most of its energy from coal and the country is pushing for a declaration to ensure a "just transition" from fossil fuels.Dozens of protesters picketed a former coal mine near the site of the two-week summit - in Katowice - to express anger over the government's reliance on fossil fuels.The summit received a boost over the weekend after the G20 economies affirmed their commitment to the Paris Agreement.Image:Poland still gets the majority of its energy from coalAmerica, however, controversially withdrew from the deal after it was criticised by US President Donald Trump.

There are also fears that Brazil's new president, Jair Bolsonaro, could follow suit.An estimated 65,000 protesters turned out in the Belgian capital on Sunday for the "claim the climate" march.They urged leaders to take dramatic action and chanted slogans including "there is no planet B" and "climate first, politics second". 1:32 Video:Are we doing enough about climate changeUN General Assembly president Maria Espinosa has said mankind is "in danger of disappearing" if climate change progresses at its current rate."We need to act urgently, and with audacity.

Be ambitious, but also responsible for the future generations," she said.The COP24 conference follows a series of scientific reports this year warning that far bigger cuts to emissions are needed than were agreed in Paris.Image:Delegates from nearly 200 countries are attending the summitThe Intergovernmental Panel on Climate Change said in October that the planet is responding faster and more dramatically to the warming atmosphere than had been predicted - and the temperature rise must now be kept to no more than 1.5C.Naturalist Sir David Attenborough will deliver a speech at the COP24 as he takes up the first ever "people's seat" at the talks - an initiative promoting the need to act on climate change.Meanwhile, three US-based environmental groups have also claimed there were twice as many meat dishes as plant-based ones on offer in the main food court of the Polish conference.Meat production requires far more water and land, and causes significantly higher greenhouse gas emissions than vegetarian options.The Center for Biological Diversity, Farm Forward and Brighter Green said that if all meeting participants choose meat dishes, it would be the equivalent of burning half a million gallons of gasoline.Their calculations could not immediately be independently verified.