Hit and myths

Charlie Mitchell debunks two common climate change claims.

MYTH:

The Earth would have been warming anyway, humans are just adding to it.

The myth that natural variability in the Earth’s climate is partly responsible for recent global warming is a common one. The truth, however, is it’s likely nearly all of the warming since 1950 can be attributed to humanrelated greenhouse gas emissions. The most recent US National Climate Assessment, released in 2017, estimated between 93 per cent and 123 per cent of warming between 1951 and 2010 was caused by humans, meaning it’s possible that without human-related greenhouse gas emissions, Earth would be on a slight cooling trend, due to natural factors such as volcanic eruptions and solar activity. A similar conclusion was found in the Intergovernmental Panel on Climate Change’s last major report in 2013.

BUSTED:

over unusually warm seawater, and coincided with northerly winds and a king tide. The result was the highest sea-level recorded in Thames since at least 1938.

A few weeks later, a similar situation happened along the Tasman coast, near Nelson – Fehi became much more damaging when it arrived at a particularly high tide, causing storm surges to flood seawalls.

A higher sea means coastal flooding becomes more common, to the point where it will become the major source of flood damage in the coming decades.

‘‘Waves, tides, everything are riding on the back of this higher baseline sea-level,’’ Bell says. ‘‘By the middle of this century, as sea level increases, coastal

MYTH:

Sea-levels have only risen around 20cm over the last century, so there’s nothing to worry about.

It’s true that the sea has risen, on average, around 20cm over the last century in much of the world, including New Zealand. But the rate of sea-level rise is not static, and the past rate tells us little about the future rate: the sea is rising much more quickly, and will continue to do so in the coming century, and potentially beyond. The most recent measurements around New Zealand show the sea is rising around 3-4mm a year, twice as fast as the average rate for much of the 20th century. Experts expect that rate to continue to accelerate. Sealevels are among the slowest responders to climate change, but also among the most reliable indicators of a warming climate.

The last time the Earth was 2C warmer than the pre-industrial era (the target under the Paris Agreement), the seas were 5m higher than today, and likely rose to that level over thousands of years.

BUSTED:

flooding will become the dominant coastal hazard risk. Once you start to get to half a metre or so, extensive areas will get flooded.’’

New Zealand will be spared some of the most severe impacts of a warmer climate – like extreme high temperatures – but is particularly exposed to sea-level rise. It has the world’s ninth longest coastline, and millions of people live within 5km of the coast.

More than three-quarters of the major population centres are coastal, and tens of thousands of people live within 50cm of the mean high-tide mark, the area most at risk of sea-level rise. New Zealanders love the coast,