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Big Drop In Solar Activity Could Cool Earth
coondoggie writes "Scientists say the Sun, which roils with flares and electromagnetic energy every 11 years or so, could go into virtual hibernation after the current cycle of high activity, reducing temperatures on Earth. As the current sunspot cycle, Cycle 24, begins to ramp up toward maximum, scientists from the National Solar Observatory and the Air Force Research Laboratory independently found that the Sun's interior, visible surface, and corona indicate the next 11-year solar sunspot cycle, Cycle 25, will be greatly reduced or may not happen at all."
Decreased solar output will have an impact on global temperatures, but it will take time.
Greenhouse gasses (Water, CO2, CH4, etc) do not directly interact with incoming shortwave radiation from the sun. Rather, they interact with the longwave radiation coming from the surface of the Earth. With no greenhouse gasses, the Earth would radiate (based on its temperature) and this radiation would be lost to space. What greenhouse gasses do is absorb the emitted longwave which adds energy to the molecule absorbing it. The excited state either results in a temperature increase of the molecule, or the emission of radiation. Some of this re-emitted radiation is directed downward, toward the Earth. The net result is that some energy that would be lost to space is absorbed by molecules in the atmosphere, warming it, and some is redirected back to the Earth, increasing the net incoming radiation.
The effect can be directly observed. If you look at the measured longwave radiation emitted at the top of our atmosphere, the global average temperature you would calculate would not support life as we know it (much too cold). The difference from that and our directly observed average surface temperatures are due to the greenhouse effect (the energy based on those temperatures is not making it to the top of the atmosphere).
Decreasing solar input would change part of the energy budget, but the greenhouse effect will act as a buffer (from absorbing and re-emitting longwave radiation) that would cause a delayed response.
Note that I am not a climate scientist, just a regular meteorologist who has taken a few classes in radiative transfer.
Solar activity had nothing to do with "The Year Without a Summer". It was the eruption of Tambora that caused that.
And they're going to be sorely disappointed when the warming continues despite reduced solar output.
Even if the Sun went into a new Maunder Minimum Global Warming will continue because the forcing from increased GHG's (primarily CO2) overwhelms the change in insolation. There is a peer reviewed paper on the subject here: On the Effect of a New Grand Minimum of Solar Activity on the Future Climate on Earth (Feulner & Rahmstorf 2010).
So what will the "naysayers" response be to continued warming despite reduced insolation?
Criticism usually includes putting forth an alternative model. Not just shouting "NO! NO! NO!". The basic forcing by CO2 is a simple physical fact - every 2nd semester student can do the math. The effect is measurable, just take a spectrum. Did that myself, ages ago in a physical chemistry lab session. Measuring the increase in atmospheric CO2 is trivial. Proving that the increase is anthropogenic is trivial - just look at the isotope ratio. Measuring solar input is trivial. These are the basic forcings. Now, the feedbacks and the amount of their contribution is open, I give you that - but the basic fact of warming due to CO2 is simply not open to debate any more.
Ubi solitudinem faciunt, pacem appellant.