See what Dec 2015 to Feb 2016 looked like, temperature-wise:
2016 started off way hotter than 2015. A sudden jump like this is called a step change. If you expect we'll now cool off to our previous decadal average, forget that. We've "leveled up".
The current warming surge amounts to what’s called a step change — a practically instantaneous shift in our planet’s climate.
This sudden shift in temperature has arrived because of a confluence of events: Long-term global warming, the multiyear effect of El Niño, and extreme weather — including persistent heat waves at the regional scale.
The major cause of February’s exceptional warmth is global warming,…
… El Niño can’t explain all or even most of the current warming spike — especially the warmth in the Arctic.
Based on the Met Office’s estimates and my calculations, 2016 will probably be around 1.1 to 1.5 degrees above the 1850-1900 average. An annual breach of 2 degrees could happen as soon as 2030, according to climate model simulations,…
According to a five-year prediction from the Met Office, global temperatures may fall slightly over the next year or two, as the El Niño wanes and temporarily cooler ocean temperatures associated with La Niña take hold. But global warming will make that respite brief: 2018, 2019 and 2020 will likely be warmer than 2015, and the warming trend is expected to continue long after that. Sixteen of the 18 years that followed the last big El Niño (1997-98) were warmer than 1997. [emphasis mine]
Step changes also happen in other climate issues, such as the rate of sea level rise. Sudden jumps in the rate of melt indicate a tipping point was passed, and new self-reinforcements have kicked in.
Doubling times in non linear events often don’t fit a pure exponential curve — instead tending to follow a series of spikes and recessions with major transitional events coming at the end of any ‘curve.’ [emphasis mine]
Our path ahead: major transitional events kicking us into new regimes of change we'll hate.
Processes of vegetation water-stress and soil moisture are not adequately modeled in current climate science. Julia Greene and Pierre Gentine's study found that the ability of land plants to absorb carbon has been halved already by swings in soil moisture from droughts and heat waves. Their model suggests that by mid-century land carbon absorption will drop enough to, by itself, cause a large increase in CO2.
"It is unclear ... whether the land can continue to uptake anthropogenic emissions at the current rates,"...
... Gentine and Green analyzed net biome productivity (NBP), … equal to the net ecosystem production minus the carbon lost from disturbance like a forest fire or a forest harvest.
They were able to isolate the effects of changes in long-term soil moisture trends (i.e. drying) as well as short-term variability (i.e., the effects of extreme events such as floods and droughts) on the ability of the land to uptake carbon.
"We saw that the value of NBP, in this instance a net gain of carbon on the land surface, would actually be almost twice as high if it weren't for these changes (variability and trend) in soil moisture," says Green ...
"This is a big deal! If soil moisture continues to reduce NBP at the current rate, and the rate of carbon uptake by the land starts to decrease by the middle of this century -- as we found in the models -- we could potentially see a large increase in the concentration of atmospheric CO2 and a corresponding rise in the effects of global warming and climate change." [emphasis mine]
Eight of the next-generation climate models being developed to produce the United Nation's 2021 Climate assessment are predicting significantly higher climate sensitivity than past models, around 5 degrees C for CO2 doubling.
Modelers are struggling to identify which of their refinements explain this heightened sensitivity...
But the trend “is definitely real. There’s no question,”says Reto Knutti, a climate scientist at ETH Zurich in Switzerland.
The new simulations are only now being discussed at meetings, and not all the numbers are in, so “it’s a bit too early to get wound up,” says John Fyfe, a climate scientist at the Canadian Centre for Climate Modelling and Analysis in Victoria, whose model is among those running much hotter than in the past. “But maybe we have to face a reality in the future that’s more pessimistic than it was in the past.”
The sixth CMIP is now at least a year late.