The Pope and James Hansen: Are these moral and scientific tipping points?
James Hansen’s Latest Paper: Ice Melt, Sea Level Rise and Superstorms
As an unabashed fan, I read Dr. James Hansen’s latest paper, Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2ºC Global Warming is Highly Dangerous, the day it was published. I encourage everyone to read it and join this conversation in the comments.
Here are my takeaways:
The notion that 2ºC rise in global mean temperature is safe is nuts.
The paper describes the Earth’s Eemian period, where temperature was about 2ºC warmer than preindustrial temperatures, or about 1ºC warmer than today. Geologic evidence suggests sea level may have been as much as 9 m higher and that sea level changes were rapid. The Eemian tells us we could experience 5 – 9 m sea level rise at 2ºC. Given the modern consequences of such a rise in sea level, the 2ºC temperature rise limit asserted at COP 15 in the Copenhagen Accord (2009) is NOT safe.
Sea level is already rising, but faster than thought.
For the ~75% of people who realize sea is rising, the problem expressed in millimeters seems distant and benign. Data from my favorite NOAA metering station shows a linear fit to the local sea level data.
A lot of engineering and planning was done, and still is done, using linear extrapolations of data like this.
Figure 29 in the paper shows the rate of global sea level rise more than doubling since 1993.
Mind you, both of the above graphs are based on observations, not outputs of climate models. Even while the rate of sea level rise is shown to double, Hansen and colleagues make the case that other processes affecting sea level rise understate changes in the rate of melt of the Greenland and Antarctic ice sheets. That’s important to know for the next idea.
The rate of ice melt in the Greenland and Antarctic ice sheets is predicted to double.
Climate model runs by Dr. Hansen and his colleagues suggest the rate of ice sheet melt will double in the next 10 to 40 years. The doubling in melt rate seems almost certain. The question seems to be more of how soon, with odds favoring earlier in the 30 year window.
Consistent with the increased melt rate, the climate models show massive influxes of fresh melt water near Greenland and Antarctica. The paper explains, in painful detail, the consequences of the massive fresh water influx.
Are you sitting down? You really should sit for the next one.
Global surface air temperatures are predicted to fall (and then rise).
In response to ice sheet melt, and with cruel irony, the climate models predict surface air temperatures will dip for periods as a result of the accelerated melt and resulting influx of freshwater into the ocean.
Figure 10 shows potential timing and magnitude of global surface air temperature depending on the timing of the ice melt doubling discussed above.
Dr. Hansen points out that if these predicted surface air temperatures are correct, then temperature alone is not a good indicator for tracking the impacts of climate change!
I shudder when imaging the climate change denial machine running headlines like ‘climate change experts (former global warming experts) now say temperature will fall!’
Dr. Hansen and his 16 co-authors are brutally frank.
When I have met him in person, I have found Dr. Hansen to be soft-spoken and very affable. I have difficulty imagining words from him that are not gentle.
Don Bain, Dr. James Hansen, and Lauren Bain at West Chester University, 2014.
In scientific journals, the norm is understatement. But, when I read these prestigious authors’ words, I am startled:
“Our analysis paints a different picture than IPCC (2013) for how this Hyper- Anthropocene phase is likely to proceed if GHG emissions grow at a rate that continues to pump energy at a high rate into the ocean. We conclude that multi-meter sea level rise would become practically unavoidable. Social disruption and economic consequences of such large sea level rise could be devastating. It is not difficult to imagine that conflicts arising from forced migrations and economic collapse might make the planet ungovernable, threatening the fabric of civilization.”
Setting aside the clown-like politics and short-term myopia of today’s public media attention, we have to recognize a truly messy, scary and Earth-shattering slow motion train wreck unfolding. Slowly, we are going to realize what we are doing to our planet and the future we are committing to our children.
Although the scientific community’s reaction to this new paper is still extremely preliminary, you can find some initial comments here: