Climate Explained: what Earth would be like if we hadn’t pumped greenhouse gases into the atmosphere
UC Environmental Physics lecturer Laura Revell contributes to new article series Climate Explained on The Conversation.
Revell answers two similar questions; if humans had not contributed to greenhouses gases in any way at all, what would the global temperature be today, compared to the 1800s before industrialisation?
and, what happens when all the greenhouse gases are eliminated? What keeps the planet from cooling past a point that is good?
Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.
The diameter of Earth is 12,742km and the atmosphere is about 100km thick. If you took a model globe and wrapped it up, a single sheet of tissue paper would represent the thickness of the atmosphere.
The gases that make up Earth’s atmosphere are mostly nitrogen and oxygen, and small quantities of trace gases such as argon, neon, helium, the protective ozone layer and various greenhouse gases – so named because they trap heat emitted by Earth.
The most abundant greenhouse gas in Earth’s atmosphere is water vapour – and it is this gas that provides the natural greenhouse effect. Without this and the naturally occurring quantities of other greenhouse gases, Earth would be about 33℃ colder and uninhabitable to life as we know it.
Since pre-industrial times, human activities have led to the accumulation of greenhouse gases such as carbon dioxide, methane and nitrous oxide in the atmosphere. The concentration of atmospheric carbon dioxide has risen from about 280 parts per million (ppm) before the first industrial revolution some 250 years ago, to a new high since records began of just over 417ppm. As a result of continued increases, the global average temperature has climbed by just over 1℃ since pre-industrial times.