7 Dec 2015

What you need to know about climate change

1:54 pm on 7 December 2015

Leaders from across the globe are currently gathered in Paris for COP21 with a goal to try and tackle one of earth’s biggest problems: global warming. 

It seems there’s still a whole lot of myths out there about climate change though, so we’ve debunked a handful of them below. Let’s get to the truth.

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Myth 1: Extreme weather has always happened. Humans can’t be responsible for the changes going on now.

It’s true that big storms have always happened, and it will keep happening, but thanks to the carbon dioxide we’ve already added to the atmosphere they will happen more often, and be more furious.

Extra CO2 has warmed the atmosphere by about 1 degree Celsius, on average, with some areas of the globe warming more, others less. Warmer air holds more water, so its potential to dump torrential rainfall has increased.

In June this year, New Zealand experienced a few examples of extremely heavy rainfall. Whanganui, Palmerston North and Central Otago had to deal with rainfall within two days that was more than double the June normal, while Dunedin was drenched in more than three times its normal total for this time of year.

Already, the humidity levels in the atmosphere have gone up by 5 per cent, and New Zealand's position relative to the subtropics makes these islands particularly exposed to the impacts of a warming climate.

In the words of NIWA’s chief scientist for climate, atmosphere and hazards, Sam Dean:

“As the atmosphere in the subtropics warms, it holds more water, gets sucked down and slams into New Zealand. It's one of the most robust responses of climate change.”

Myth 2: Scientists disagree over whether climate change is real.

Ninety-seven per cent. It’s possibly one of the most quoted and debated figures in climate change.

Multiple studies have looked at how many scientists agree that climate change is happening and that we are causing it, and they’ve come up with this number to describe the near-consensus on the issue.

NASA has also compiled a (not comprehensive) list of scientific organisations that have made clear statements on climate change and our role in it, and in September this year, another study showed that the climate change consensus extends beyond those working directly on the issue, with 94 per cent of scientists working on completely different topics also agreeing that temperatures are rising and that we’re to blame.

Unequivocal.  That’s another way of describing the overwhelming agreement on the causes and impacts of climate change in the science community, as is this statement, published in the Synthesis Report of the most recent assessment by the Intergovernmental Panel on Climate Change.

“Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.”

Another answer is that there is evidence coming from a bunch of different place: From ice cores, to pollen analysis, tree rings, corals, sea level rise and, last but not least, the unprecedented (in the time that humans have lived on this planet) increases in carbon dioxide in the atmosphere all point to a singular conclusion. The planet is warming and will continue to do so unless we stop adding greenhouse gases to the atmosphere.

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Myth 3: Antarctica has more ice than it used to.

Antarctica has so many different kinds of ice that it comes with its own vocabulary.

Massive ICE SHEETS cover the continent. Antarctica has two of them – the larger East Antarctic Ice Sheet (EAIS), which is 4 kilometres thick in places and buries entire mountain ranges underneath, and the smaller West Antarctic Ice Sheet (WAIS), which binds together a number of smaller chunks of land.

ICE SHELVES are huge slabs of floating ice that flow off the continent and stretch out across the ocean. The largest of these, the Ross Ice Shelf, is the size of France.

Apart from these two types of mega-sized icy landforms, there are much smaller features, including glaciers, domes and ice streams.

All of these icy bits above are either sitting on land or connected to land, and they are losing mass – in some places quickly, and irreversibly.

But Antarctica also features SEA ICE, a relatively thin (two or three metres maximum in thickness) blanket of ice that surrounds the continent – and this is the part that has been growing recently.

Sea ice comes and goes with the seasons in one of the most spectacular environmental changes on the planet. In autumn, the ocean around Antarctica literally begins to freeze and the ice spreads out into all directions, until, at its peak, it doubles the size of Antarctica.

Then, come spring, it all melts again. Because sea ice floats on the ocean, its freeze-thaw cycles make no difference to sea level rise, but it plays an important role as a climate regulator (think big shiny surface that reflects the sun’s energy back into space) and as a habitat for penguins and seals (Emperor penguins breed on sea ice, forage from chunks of sea ice – they can’t survive without it).

There are a number of reasons why the overall area of Antarctic sea ice has been growing in the last few years, despite the fact that the Southern Ocean has been warming.

One of them is that the ozone hole has strengthened the circumpolar winds, known as the polar vortex, and another is a change in ocean circulation. The latter is a complex sequence of events, but in short, warmer air brings more rain and snowfall, which freshens the surface waters, which in turn means that the surface waters mix less with the saltier, heavier and warmer waters below, and if less of the warmer water comes to the surface, the sea ice doesn’t melt as quickly as it used to.

Myth 4: A 2 degree rise in temperature is safe.

Back in 2010, at an earlier COP meeting held in Cancun, Mexico, negotiators agreed that we should do our best to keep warming under two degrees Celsius above pre-industrial times, and to aim for 1.5 degrees.

This remains an important goal at COP21 in Paris, but the emissions reduction pledges countries have made so far fall rather short of it. It will take an ambitious effort to start bringing emissions down quickly and strongly enough for the world to stay below the two-degree limit.

“Two degrees” quickly turned into shorthand for a safe limit, but the reality is far from it. We’re now at a half-way point, and already we’re seeing rising seas, more frequent and damaging floods, and extreme weather events. For people living on low-lying islands such as Tuvalu, Kiribati or the Marshall islands, a two-degrees warming could mean the loss of their homelands.

Marshallese poet Kathy Jetnil-Kijiner addressed the COP21 meeting by reciting from her poem Two Degrees.

Myth 5: New Zealand would be better off if the climate was warmer.

We will have warmer winters and that could be good news for people living in houses that are not built for cold and damp conditions, but apart from that most of the consequences of warmer temperatures will be disruptive.

For starters, warmer air means more violent storms and more torrential rain.

A warmer climate also means more wildfires in some parts of New Zealand, longer and more intense drought, and changes to seasonal crop cycles.

A warmer ocean means rising seas (warmer water takes up more space, expands), shifting currents and changing habitats for marine life.

Should the world decide to implement the most ambitious measures to bring greenhouse gas emissions to zero over the next 50 to 80 years, New Zealand’s overall temperature will nevertheless rise by about another 0.8°C this century before it finally starts heading back down. In a high-carbon world, it could climb to somewhere between three to five degrees above the current average.

Myth 6: New Zealand is too small to make any difference to the global climate.

As a nation, New Zealand contributes less than 1 per cent of the world’s greenhouse gas production, and some have argued that whatever we do to reduce our emissions won’t make much difference.

But the same argument could be made for any group of 4.5 million people, wherever they live.

A more accurate reflection of our contribution to climate change is the emissions we produce per head of population, and on that measure, we are right up there with some of the biggest polluters, not far behind the United States, Australia and Canada.

Myth 7: There is no connection between eating meat and climate change.

This might spoil the barbeque season, but if you want to do something good for the climate, quitting steak will make a difference in two ways.

It takes a lot more energy, land and water to grow a cow than it takes to grow vegetables, and red meat and dairy products account for about half of a household’s food-related emissions. Cutting down on the number of days you have meat or dairy can make a significant dent into your emission budget.

The second reason is that cows (and sheep) burp methane, which is a potent greenhouse gas (more potent than carbon dioxide but it doesn’t stay in the atmosphere for as long as CO2). New Zealand’s greenhouse gas emissions profile is quite different from other developed countries because of the contribution from agriculture. About half of our emissions come from the primary sector, and most of that is methane from ruminant (belching) livestock.

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Scientists have come up with ways that could reduce methane emissions dramatically, but even then, the first reason still holds true. Red meat has a bigger carbon footprint than vegetarian foods, so eating less will make a difference.

Recently Motu, a not-for-profit research institute on economic and public policy, looked into how individuals can help reduce emissions, and eating less red meat and dairy was among one of the most effective ways to make a difference.

Motu came up with this haiku to some up their findings:

Cars, planes, red meat, milk
I can reduce my impact
Can you reduce yours?

Apart from helping to save the planet, eating more vegetables and less meat will likely do your health some good, too.

Veronika Meduna is a producer for RNZ's Our Changing World science show and author of the book Towards A Warmer World: What Climate Change Will Mean For New Zealand's Future.