bIn April 2006, the American PBS network screened the documentary “Dimming the Sun” about the (then) newly discovered phenomena of “global dimming.”
The documentary claimed that global dimming, where man made pollutants such as soot, ash and sulphur particles in the atmosphere block out solar energy (and also change the quality and type of cloud cover, further blocking solar radiation), had likely fooled scientists into underestimating how powerful the global warming effects of greenhouse gas emissions actually are.
I presume most of this documentary was filmed and written in 2005/early 2006, ten to eleven years ago. My takeaway: now that an entire decade has rolled by, we have fallen into that very human trap of conveniently moving the goal posts and fooling ourselves into thinking that we still have tomorrow to make our ‘real’ move, because, ahhh serious climate change is still avoidable. Just think positive and be inspired!
When in reality the timer to successfully change the course of our civilisation probably ran out quite some time ago.
At the time of the doco, Jim Hansen was a head scientist with NASA. He is currently with Columbia University.
This is a copy and paste of different sections from the documentary transcript:
JAMES HANSEN: Our estimate for the particle forcing is minus-one-and-a-half-watts- per-meter-squared. So that would imply a cooling of more than one degree Celsius.
NARRATOR: In other words, while the human greenhouse effect has produced 2.6 to three watts of extra energy for every square meter of the Earth, global dimming has subtracted about 1.5 watts, so, more than half the warming effect of our greenhouse emissions has been masked by the cooling effect of particle pollution.
Perhaps this is why, despite a large rise in the concentration of greenhouse gases, until recently, the temperature rise has been hard for most of us to notice.
PETER COX: We’re going to be in a situation, unless we act, where the cooling pollutant is dropping off while the warming pollutant is going up. CO2 will be going up and particles will be dropping off, and that means that we’ll get an accelerated warming. We’ll get a double whammy. We’ll get reducing cooling and increased heating at the same time, and that’s, that’s a problem for us.
JAMES HANSEN: If the particle forcing is what we estimate, about minus-1.5 watts, that would imply that removing that forcing would cause a global warming of more than one degree Celsius. That’s more than the warming that we’ve seen already, so this is a huge factor.
NARRATOR: If we continue as we are, combining reduced air pollution with an increase in greenhouse gases, temperatures could rise by a further two or even three degrees Celsius. That’s as much as five degrees Fahrenheit by mid-century, much sooner than current models predict.
JAMES HANSEN: But, in my opinion, three degrees Celsius is not the level of dangerous interference; that’s the level which guarantees disaster.
JAMES HANSEN: I think we have less than a decade to avoid passing what I call “point of no return.” I think we have to keep global warming less than one degree Celsius, or we’re going to get very bad effects. And the problem is that to achieve…to keep the warming less than one degree Celsius, we have to level off the emissions and get them to decline before the middle of the century, substantially.
Right now, the course that we’re on—plus 2 percent per year in greenhouse gas emissions—well, if you continue that, even for 15 years, it’s a 35 percent increase. And then there’s no way that you could possibly meet this alternative scenario with warming less than one degree Celsius.
I bolded and italicised Hansen’s comment above:
I think we have less than a decade to avoid passing what I call “point of no return.” I think we have to keep global warming less than one degree Celsius, or we’re going to get very bad effects.
To recap: he made that statement just over one decade ago.
And at the time of this documentary the scientists interviewed said that climate warming 0.6-0.8 deg C above the historical norm had been observed. And that anything over 1 deg C warming was going to lead to “very bad effects” (James Hansen).
Remember those numbers. 0.6 deg C to 0.8 deg C of warming seen back in 2005/2006.
Well, Bill in his recent post “Nice weather down here” noted that NASA had reported April land and sea temperatures that were 1.29 deg C above the historical average.
Yes, that’s only 0.6 deg C warmer in 10 years, and of course, April was probably just a rogue high. Like March before it, February before it, January before it, December before it,…you get the idea.
Then think about another 0.6 deg C increase in the next ten years. With the emissions already in the air today, that kind of rise is already “baked in” regardless of what we choose to do or not do.
In other words, my pick is that we will see almost 2 degrees C of warming not by 2100, but in the 2020s. And if we ever significantly take down the cooling particulate pollution that we are pushing into the air, we will see another degree C of warming on top of that within literally days. (I refer to the research mentioned in the documentary about the measurable temperature changes which occurred across the entire USA when all aircraft were grounded for the 3 days after 9/11).
I encourage everyone to read the documentary transcript I linked above in full. Or watch the full ten year old doco here: