Posts Tagged ‘uncertainties’

by Andrew*

Question: What is the biggest constraint on reducing climate uncertainties?
Many uncertainties about how the planet will react to a future anthropogenic warming still exist. It is of critical importance that we reduce these uncertainties as much as possible and as fast as possible. So what do you believe is holding us back the most?

Is it lack of sufficient computing power? Lack of observational data? Lack of brain power (e.g. fundamental theory)? Something else?

Phrased differently: If you had $ 50 million to put towards the sole goal of reducing the uncertainty of one specific climate variable, how would you spend it? And which specific uncertainty would your investment aim to tackle?

Answer:

Answer by Ottawa Mike
I’m going to say observational data. It seems to me that it’s hard to identify, hard to collect, hard to adjust and hard to interpret. And if I had $ 50M to help out, I’m not even sure how to improve the situation. The timescales involved and the precision needed seems daunting.

So I can’t see how certainty can be improved until we have a firm grasp of good observational data which would allow us to hypothesize more accurately.

It may also turn out that long range climate forecasting is as chaotic as short term weather forecasting so there might not be anything we could about predicting it even if we poured all the money in the world into studying it.

Question by Trevor: What are some genuine uncertainties regarding climate change?
It’s widely accepted that human activities are impacting upon the climate and this is supported by reconstructed, observational and empirical evidence. Within the climatic systems there are many inherent complexities and uncertainties. There are known inconsistencies and apparent contradictions and of course, there is much that we don’t fully understand.

What do you consider to be the uncertainties regarding climate change, what are the inconsistencies and in which specific areas do you feel a greater comprehension would be of significant benefit?

Best answer:

Answer by Dana1981
Climate sensitivity. Although climate scientists have constrained it pretty well to within 2–4.5°C warming for a doubling of atmospheric CO2, and a most likely value of 3°C, the precise value is still a genuine uncertainty, and important to determine. We’re probably going to reach that 560 ppm CO2 concentration this century (unless we take serious steps to avoid it, which thus far we have not), and knowing whether that means 2°C or 4.5°C or somewhere in between is important.

Feedbacks. Knowing when significant amounts of methane will be released from melting permafrost or the oceans or warming peat bogs, for example. Or when the ocean will become saturated with CO2. Or….

Water vapor. Will relative humidity remain constant, as is assumed in climate models?

Cloudcover. How will different types change in response to a warming world, and will this make cloudcover a net positive or negative feedback?

Adequate Response. How much do we need to reduce anthropogenic CO2 emissions to avoid triggering these feedbacks and causing highly dangerous warming?

Policy Measures. What would be the most effective policy to successfully reduce emissions and atmospheric CO2 (cap and trade, cap and dividend, carbon tax, government regulation, geoengineering etc.)?

I think it’s important to point out a few things.

1) The cause of the current warming is not a significant uncertainty. The IPCC puts the probability that the current warming is dominantly anthropogenic at greater than 90%, and that’s a conservative value. I’d say 99% would be more accurate at this point.

2) Uncertainty can’t be used as justification not to act. For example, for those who want to argue that lower values of climate sensitivity can’t be ruled out (i.e. Lindzen and Spencer), that also means high values can’t be ruled out. It’s just as likely that climate sensitivity to CO2 doubling will be 6°C as it is that it will be 1°C. If you’re arguing for high uncertainty, you’re also arguing that catastrophic results are entirely possible, and therefore that we must act to prevent this possibility.

What do you think? Answer below!

Due to uncertainties in projected climate changes and in how systems respond to those changes, adaptation options offer varying degrees of uncertainty,or risk if you will.

No-regret: Actions that make sense or are worthwhile regardless of additional or exacerbated impacts from climate change.

Opportunity: Actions that capitalize on observed or projected climatic changes. The proactive farmer who switches to a more adaptative crop, for example.

“Win-win”: Actions that provide adaptation benefits and meet other social, environmental, or economic objectives.

Low-regret: Measures with relatively low costs for which benefits under climate change scenarios are high, like factoring climate change into public land management policies.