Climate change in Metropolitan Sydney

Across the Metropolitan Sydney  region, average temperatures are projected to rise throughout this century under all emissions scenarios. The main difference between scenarios is the scale of change: lower emissions show slower and more moderate increases, while higher emissions lead to a greater and ongoing rise in average temperature.

Under a low-emissions scenario, the rate of average temperature increase is expected to slow around the middle of the century. Under medium- and high-emissions scenarios, temperatures are expected to keep climbing past the middle of the century with no sign of levelling off by the end of the century, with faster and greater increases under a high-emissions scenario. 

These changes are expected to be felt fairly evenly across the region. Inland areas like Penrith and coastal areas like Cronulla are projected to experience comparable rises in average temperature under low-, medium-, and high-emissions scenarios.

Across the Metropolitan Sydney  region, the number of hot days is projected to increase throughout this century under all emissions scenarios. The main difference between scenarios is the scale of change: lower emissions show slower and more moderate increases, while higher emissions lead to a greater and ongoing rise in the number of hot days.

Under a low-emissions scenario, the rate of increase is expected to slow around the middle of the century. Under medium- and high-emissions scenarios, the number of hot days is expected to keep rising past the middle of the century, with no sign of levelling off by the end of the century, with faster and greater increases under a high-emissions scenario. 

Both inland and coastal parts of the region will see hot days increasing at a similar pace. Coastal areas like Cronulla will have more hot days than they do now, but still fewer than inland areas such as Penrith in Western Sydney. Because Western Sydney already starts out with more hotter days, it will see the biggest overall jump in the total number. Wherever you live in Metropolitan Sydney, summers will feel hotter than they do now.

There will be noticeably fewer cold nights in Metropolitan Sydney this century. The main difference between scenarios is the pace and size of the decline: lower emissions slow the change, while higher emissions lead to faster and greater losses.

Under a low-emissions scenario, the decline of cold nights slows around the middle of the century. Under a medium- and high-emissions scenarios, the number of cold nights continues to decline past the middle of the century, with no sign of levelling off, and by the end of the century the region could have very few, if any, cold nights under a high-emissions scenario.

The biggest changes in the number of cold nights will occur in higher-elevation inland areas that currently experience many cold nights, such as Blackheath in the Blue Mountains. Coastal areas in the region such as Cronulla will see little or no change because they already have few, if any, cold nights. This means that while inland areas will still have more cold nights than the coast, the difference between them could shrink as cold nights become less common across the whole region.

Annual average rainfall in the Metropolitan Sydney region is projected to remain variable throughout this century but is projected to decline under all emissions scenarios. The main differences between scenarios are in how large the reductions are and when they occur.

By the middle of the century, the high-emissions scenario shows a noticeably greater drop in annual rainfall than the low- and medium-emissions scenarios. By the end of the century, the differences between scenarios change their behaviour, rainfall continues to decline under the low- and medium-emissions scenarios, while the high-emissions scenario shows a slight increase in rainfall from the middle of the century but still remains below current levels.

Projections show the greatest decreases will occur in winter, the season that already has the least rainfall. Inland areas such as the Blue Mountains and Western Sydney are projected to experience the greatest decreases in average winter rainfall. Blackheath in the Blue Mountains is expected to see a larger reduction than coastal areas like Cronulla, where winter rainfall is also projected to decrease but to a lesser extent.

Across the Metropolitan Sydney  region,  the number of severe fire weather days is projected to rise throughout this century under all emissions scenarios. The main difference between scenarios is the scale of change: lower emissions show slower and more moderate increases, while higher emissions lead to a greater and ongoing rise in number of severe fire weather days. 

Under a low-emissions scenario, the rate of increase is expected to slow around the middle of the century. Under medium- and high-emissions scenarios, severe fire weather days are expected to keep climbing past the middle of the century with no sign of levelling off by the end of the century, with faster and greater increases under a high-emissions scenario.

Both inland and coastal parts of the region will see the number of severe fire weather days increasing at a similar pace. Coastal areas like Cronulla will have more severe fire weather days than they do now, but still fewer than inland areas such as Penrith in Western Sydney. Because Western Sydney already starts out with more severe fire weather days, it will see the biggest overall jump in the total number. Wherever you live in Metropolitan Sydney, severe fire weather days will become more likely.