These climate changes are caused by human activities: mainly from increasing levels of greenhouse gases. The world has warmed by ~1.0°C, whilst carbon dioxide levels (our main greenhouse gas) have risen by nearly 50% since preindustrial times. This change in carbon dioxide is already greater than the difference seen at the depth of the last ice age. But, not only are humans still emitting additional carbon dioxide to the atmosphere, our emissions are growing not reducing.
Responses to climate change fall into two categories: dealing with the cause of the problem (technically termed “mitigation”) and coping with the changing climate (“adaptation”). The world’s governments’ negotiated the Paris Agreement in 2015, which aims to hold “the increase in the global average temperature to well below 2°C above pre-industrial levels”.
The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. All the work done by scientists is voluntary. More than 830 Authors and Review Editors from over 80 countries were selected to form the Author teams that produced the Fifth Assessment Report (AR5). They in turn drew on the work of over 1,000 Contributing Authors and about 2,000 expert reviewers who provided over 140,000 review comments. NASA has an excellent website on climate change.
As Brigadier General Stephen Cheney, US Department of State’s foreign affairs policy board, said in Dec 2016:
“Climate change could lead to a humanitarian crisis of epic proportions. We’re already seeing migration of large numbers of people around the world because of food scarcity, water insecurity and extreme weather, and this is set to become the new normal.”