Under the impulse of the Intergovernmental Panel on Climate Change (IPCC), established in 1988, a consensus has been reached that true climatic change is happening within our lifetimes, is linked to global warming by human-induced greenhouse gas, principally CO₂, emissions and is accelerating.
More info on the IPCC

The impacts are already visible and manifest themselves in the following ways:
• Ice-cap melting raising sea levels with increased risk to coastal areas by flooding and storms;
• Accelerated glacier and snow  melting causing diminishing and less reliable water resources for agriculture in downstream areas and reduction in areas suitable for winter tourism;
• Heat waves causing increased deaths of vulnerable people, more frequent and more intensive wildfires;
• More droughts and less predictability of crop growing seasons resulting in more crop failure;
• More extreme rainfall and storm events leading to an increase in flash floods, soil erosion/deposition and landslides;
• More frequent/widespread pests and disease outbreaks;
• Declining biodiversity;
• Ocean acidification leading to increased mortality of fish and other water-based life;
• Increasing vulnerability of poor and marginalized people, risk of civil war and mass migration.

To some extent global warming may be mitigated by the expansion of forests and other types of vegetation capturing a large part of the excess atmospheric CO₂. Moreover,  in some parts of the world, currently too cold for growing crops or raising livestock, global warming  may offer potential for expanding agriculture or for growing new crops.