Thread by @ClimateBen

“I would think of the summer ice disappearing as the true tipping point we’ve all been afraid of..."

Veerabhadran Ramanathan, Scripps Institution of Oceanography, discoverer of role of CFCs in amplifying global warming and destroying the ozone layer

1/
washingtonpost.com/energy-environ…

'The reason Arctic ice is shrinking so fast, and why scientists are worried about it continuing, is one and the same.

There is a well-known feedback loop in the Arctic, caused by the reflectivity of ice and the darkness of the ocean.'

2/
washingtonpost.com/energy-environ…

'When the Arctic Ocean is covered by lighter, white ice, it reflects more sunlight back to space. But when there is less ice, more heat gets absorbed by the darker ocean — warming the planet further. That warmer ocean then inhibits the growth of future ice...'

3/

'The open ocean absorbs about twice as much sunlight as floating sea ice, explained Veerabhadran Ramanathan, a climate expert...

Because of this, Arctic sea ice loss has already increased the warming of the planet as a whole.

4/
washingtonpost.com/energy-environ…

'Ramanathan fears that entirely ice-free summers, if they began to occur regularly, could add another half-degree Celsius (0.9 degrees Fahrenheit) of warming on top of whatever else the planet has experienced by that time'

⚠️0.5C extra warming: horror

5/
washingtonpost.com/energy-environ…

“If that were to happen, I would think of it as an unmitigated disaster,” said Ramanathan of consistently ice-free Arctic summers. “It will quickly pump in this half a degree warming.”

A sudden rise of 0.5C would have grave consequences for most life.

6/
washingtonpost.com/energy-environ…

'That extra warming, he said, in turn could trigger a world with multiple other cascading effects, such as increasing losses of carbon from northern permafrost soil, or major damage to the Amazon rain forest.'

7/

washingtonpost.com/energy-environ…

'The additional heat would also melt snow cover over land in the Arctic, further driving up global temperatures as the darker land surface absorbs more incoming radiation.'

8/
washingtonpost.com/energy-environ…

Headed to a crucial moment:

When all of the ice in the Arctic is thin and a year old or less, we'll be 'on the verge of a much feared milestone: an entirely ice-free Arctic Ocean in summer.'

When will this occur?

The article downplays the risk here..

9/washingtonpost.com/energy-environ…

'It’s not clear how soon such an event could arrive.'

True...

10/
washingtonpost.com/energy-environ…

A recent Intergovernmental Panel on Climate Change report 'suggested it would occur once every 10 years if the globe’s total warming reaches 2°C, but only once every 100 years at 1.5°C (Warming is at 1 degree Celsius now.)'

Ok, stop.

Is this right?

11/washingtonpost.com/energy-environ…

Well, yes, the facts are correct (this is what the IPPC says).

👀However:

-in Dec 2018 warming was at 1.2C using a 1750 baseline - journalists refuse to investigate this reality

-would all scientists agree with how often ice-free summers will occur?

12/washingtonpost.com/energy-environ…

'So by the time we cross 1.5 degrees, potentially within the next few decades if warming continues, the odds of a first ice-free summer will start rising.'

This is misleading. It gives no sense that climate scientists know 1.5C could hit before 2029.

13/
washingtonpost.com/energy-environ…

Ramanathan published this key article a week before the Washington Post article came out!

It points to 1.5°C of warming between 2025 - 2030, with 2°C reached by 2045. ⚠️

Studies in the last 10 years show a first ice-free Arctic summer by 2020 - 2035.

14/nature.com/articles/d4158…

This 2013 paper could've been cited:

'We have investigated 3 approaches to predicting 21st century summer Arctic sea ice loss

time horizons for summer sea ice loss of these three approaches turns out to be roughly 2020, 2030, and 2040 respectively'

15/
agupubs.onlinelibrary.wiley.com/doi/full/10.10…

This 2016 paper, suggesting 2032 as a possible year for a first ice-free Arctic summer if carbon emissions are not seriously reduced, could have been mentioned.

16/ agupubs.onlinelibrary.wiley.com/doi/full/10.10…

Three 2020 studies now confirm that an ice-free Arctic summer in the 2020s or 2030s looks likely:

a) 2020-2049
agupubs.onlinelibrary.wiley.com/doi/full/10.10…

b) 60% chance of 2030s
penntoday.upenn.edu/news/Arctic-co…

c) satellite observations suggest 2024- 2033 (but 2040s possible):
ncei.noaa.gov/news/arctic-ic…

17/

A 2017 'Snow, Water, Ice, and Permafrost in the Arctic' study also suggested the 2030s:

🔺 disappearance of sea ice by the 2030s 'and more land ice melt than previously thought' even if the world manages to keep global warming below 2C.

18/
grist.org/article/arctic…

'As soon as the global-mean temperature has risen by slightly below 2C, the Arctic Ocean is expected to be on average nearly ice-free during September'. Sept 2018

This is perhaps why many scientists don't predict an ice-free Arctic summer before 2030.

19/link.springer.com/article/10.100…