One of the foundations of international climate change policy has been that an increase in average global mean temperature of more than two degrees Celsius is dangerous, and so climate change must be limited to below this level. But as the years have gone by and governments have done nothing, that target has been looking increasingly out of reach. And now a new paper published in Nature has confirmed the bad news: absent a radical change in policy, we're heading for four degrees:
Temperature rises resulting from unchecked climate change will be at the severe end of those projected, according to a new scientific study.
The scientist leading the research said that unless emissions of greenhouse gases were cut, the planet would heat up by a minimum of 4C by 2100, twice the level the world's governments deem dangerous.
"4C would likely be catastrophic rather than simply dangerous," Sherwood told the Guardian. "For example, it would make life difficult, if not impossible, in much of the tropics, and would guarantee the eventual melting of the Greenland ice sheet and some of the Antarctic ice sheet", with sea levels rising by many metres as a result.
Not to mention drought, famine, and the spread of tropical diseases.
What would it mean for New Zealand? Just before the holidays, the Ministry for Primary Industries published a report on Four Degrees of Global Warming: Effects on the New Zealand Primary Sector (downloadable here). The short version: live is going to get a lot harder for farmers, with more droughts and more floods (yes, they do go together). Much lower average rainfall in the east (with the models disagreeing on whether Canterbury or Hawke's Bay gets it worse), but with a general increase in extreme rainfalls (so, it rains less on average, and more of it comes in torrential downpours). River flows are expected to increase slightly (because of more rain in the west to feed them), but have a similar pattern of greater extremes (so lower low flows and bigger floods). This is expected to lead to a "pronounced decline" in pasture growth, and to lower availability of water for irrigation during growing seasons.
And our government, by refusing to act and taking an adversarial position in global climate change talks, is just letting this happen.
If we want to stop this, we need to demand action from our governments. And in many cases, that will mean changing them - because we're not going to get action from the current lot.