evidence: This small warming is likely a result of the natural alterations in global ocean currents which are driven by ocean salinity variations. [...] Scientific consensus on climate change 93 unadjusted data suggests that temperatures in Australia have only increased by 0.3 degrees over the past century, not the 1 degree usually claimed "Australia's extreme heat is sign of things to come, scientists warn". [...] Since the start of the 20th century, the global mean surface temperature of the Earth has increased by more than 0.7°C and the rate of warming has been largest in the last 30 years.