I took Rosie the truffle machine for a walk around the farm just before dark yesterday. We were both a bit stir-crazy after four days of cold, cold rain and a couple of days of screaming southerlies that brought snow to our hills. The ground passed field capacity at the beginning of last week, when an atmospheric river brought torrential downpours and flooding to much of the South Island. Now the soil is sodden, quivering with water and oozing mud at every footstep. Every drop of extra rain is taking that mud and sluicing it down to the river. A stream runs through my black truffle plantation. I spent this afternoon digging a drainage trench. Truffles don’t enjoy sitting in water. My crop might rot. The Waipara is roaring along at the bottom of our cliff at about 50 cumecs1, an impressive sight for a river that normally dribbles down to the sea at under a cumec. It peaked last week at about 110 cumecs. The riverbed will have been reshaped. But we got off lightly.
Over the last couple of days the New Zealand news has been dominated by extreme weather. The southerly storm that soaked us also battered Wellington and brought deep snow2 to much of the South Island. It made for compelling pictures. But what’s going on elsewhere in the world is even more dramatic:
The early arrival of particularly intense monsoon rain has brought flooding and chaos to northern India. At the time of writing, it is estimated that 600 people have died and 40,000 are stranded by rivers and landslides [BBC, NASA Earth Observatory, Jeff Masters.]. In The Times of India, government earth sciences secretary Shailesh Nayak was reported as saying that climate change played a role in the flooding:
The catastrophic rainfall in Uttarakhand was most likely a climate change event as it is in keeping with a pattern of increasing incidents of extreme weather events that often cause phenomenal damage as was seen in the hill state…
In Alberta, Calgary — Canada’s fourth largest city — has been flooded by torrential rains in the catchments of the Elbow and Bow rivers. Three people have died and 100,000 have been displaced. [Christopher Burt at Weather Underground, Calgary Herald, National Post, podcast: interview with Robert Sandford, ]
Meanwhile, Alaska has been experiencing a heatwave of record proportions as a slow moving giant loop in the jet stream has allowed a dome of high pressure to linger over the state.
New Zealand’s recent extreme weather was also down to a large excursion the in the southern hemisphere jet stream, as Jim Renwick told the Science Media Centre:
To get an event like this, which is pretty extreme, we need the westerly wind that normally blow across New Zealand and the southern oceans to slow down and to buckle into a series of big meanders, north-south waves around the hemisphere. […] Right now we have a series of large-scale waves around the southern hemisphere, with big southerlies near New Zealand, over the central Pacific, off the eastern South American coast, over the eastern South Atlantic, and over the central Indian Ocean. The southerly flow over/near New Zealand is the most impressive, as it reaches all the way south to south of 60S […] which is almost down to the edge of the sea ice at this time of year.
So where’s the climate change in all this? In India, Canada, Alaska and Europe we have extreme weather events happening more or less simultaneously, with a common factor — jet stream meanders — playing a significant role. Those meanders are most likely a symptom of a reduced equator to Arctic temperature differential, as Jennifer Francis and Stu Ostro explain in this recent Climate Desk event. We also have to consider the fact that the climate system is now operating at higher energy levels than before — a warmer atmosphere can carry more water vapour, and water vapour is the fuel for weather systems. More water vapour, more rain — and more intense rainfall.
Weather extremes are where the climate change rubber hits the road3. We might think that our future is described by the smoothly rising curves we see in multi-model means of global temperature projections over the next 100 years, but we don’t live in a multi-model world. We only have the one climate system, and we all live in regions, not in a notional global average.
We have to live through the noise — the bumps, the lumps, and the jumps that go with energy accumulating in the planet’s climate system. There will be more floods, more lives lost to climate instability. It’s happening now, and it’s going to get worse.
- Cubic metres per second. [↩]
- The Mt Hutt ski field got 2.8 meters of snow — just over 9 feet in the old money — a record start to the season. Take a look at the green line on their snow graph to get some sense of the context. [↩]
- And sometimes the road explodes, as happened in the recent German heatwave. [↩]