Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time.
In the 21st century, Greenhouse gas emissions keep going up. Without taking proper measures, this could have a rapid and devastating warming in the future. Unchecked global warming will not only affect polar bears and beach front homeowners, but will also cause disruption in food and water supplies. Dangerous pathogens could be spread to new areas and rising seas will have an effect on the geography. Extreme weather, worse droughts, fierce wildfires are also possible.
An agreement between nations with a long-term goal of net Zero emissions in the second half of the century will help stop global warming. Though it doesn't mean producing any greenhouse gas emissions, but limiting it to no more than the planet can absorb without raising temperatures. A transformation of world's entire energy system is required to achieve this goal. This means turning away from fossil fuels to other options like wind, solar and nuclear power.