The global average surface temperature in 2018 was between 0.9 and 1.1°C above the late 19th century average (between 1880 and 1900) (Carbon Brief 2019). The actual temperature rise for 2018 would be slightly higher if a preindustrial baseline were used. Globally, 2016 remains the hottest year on record (1.2°C above the pre-industrial era). 2017 and 2015 were both 1.1°C above pre-industrial levels (with 2015 being less than one hundredth of a degree hotter than 2017) (WMO 2018a). This made 2018 the fourth hottest year on record for surface air temperature.
The hot global average temperatures in 2018, 2017, 2016 and 2015 are part of a long-term upswing in global average temperature that began most clearly in the mid-20th century and has persisted since then. A rapidly warming world is the result of increasing greenhouse gas pollution from the burning of fossil fuels and other human activities such as land clearing. Globally, the 20 hottest years on record have occurred in the past 22 years. 2018 is the 42nd consecutive year with an above-average global temperature. No one aged under 40 has lived in a year with global average temperatures at or below the global 20th century average.
Similar trends are evident in Australia, where the average air temperature for 2018 was 1.14°C above the 1961-1990 average, making 2018 the third hottest year on record. The mean maximum temperature was the second hottest on record (1.55°C above average). It is important to note that the Australian average surface temperature refers to land only, while the global surface temperature refers to a combination of land surface and sea surface temperatures. Nine of the 10 hottest years on record in Australia have occurred since 2005 (CSIRO and BoM 2018).
Greenhouse gas pollution in the atmosphere has risen steadily since around 1750. The mean carbon dioxide (CO2) level during 2017 was 405 parts per million in the atmosphere - a 46 percent increase from the levels in 1750 (278 ppm) (CSIRO and BoM 2018). The increase in greenhouse gas pollution has led to more heat (or energy) being trapped in the lower atmosphere, raising the global average temperature by around 1°C compared to preindustrial levels (CSIRO and BoM 2018).
- The past four years have been the four hottest on record for global surface temperature, continuing a long-term warming trend.
- All extreme weather events are being influenced by climate change, as they are occurring in an atmosphere that contains more energy than 50 years ago.
- Extreme weather events are very costly, with insurance companies in Australia paying out more than $1.2 billion dollars in claims last year.