So what happens if we finally get all the climate policies into action, cut down carbon emissions, sign a global agreement and then Mother Nature throws us severe droughts, floods and other major natural disasters anyway? Why work hard to fight man-made climate change if natural climate change is going to continue regardless? It’s a fair question, so we put it to some climate scientists.

And today’s answers even involve a dash of polite disagreement. It’s like watching the peer-reviewed method in action.

Got a question about climate science? Right now at Rooted we’re running the Ask a climate scientist series. Keep the questions coming, by emailing me directly.

These answers come from American Geophysical Union’s Climate Science Q&A service, where more than 700 volunteer scientists provide factual and peer-reviewed climate science information to journalists. The AGU only comments on science, not climate policy.

Crikey reader Martin asks:

We’re often told of the severe consequences of human induced climate change — but if climate change is bad, isn’t natural climate change just as dangerous? What are the chances of us mitigating the human induced aspects, only to then be hit with some unforseen natural event (the “climate surprises” the IPCC talks of) and still have to face serious consequences?

Vincent P. Gutschick, director of Global Change Consulting Consortium Inc., responds:

“Bad” is a value judgment, assessed differently by various persons, organisations, and enterprises. We may rephrase the question to focus on changes per se and pass the findings on to stakeholders and policymakers.

That said, there is a spectrum of change. Climatic means in temperature, precipitation, storm activity and such have impacts, but extremes may be more important in very many issues. These extremes includes floods, severe storms and sudden temperature shifts, among others. Extremes can occur on long time scales, too.

The rise in atmospheric CO2 alone directly impacts plants, wildlife and agricultural, changing their photosynthetic rates, water-use efficiency, protein content, and more. It also acidifies oceans and threatens the persistence of coral reefs. The current rate of increase in CO2 exceeds all past events and is projected to have major effects on the performance, competitiveness and geographic distribution of plants.

In quantifying change, we need to distinguish changes in fundamental drivers (greenhouse gases, solar activity, parameters of the Earth’s orbit, volcanic activity) from amplifiers, modulators, and ultimate responses such as precipitation and temperature regimes, atmospheric and oceanic circulation patterns, CO2 balance of oceans and vegetation, etc.

Focusing on the fundamental drivers, there are natural and anthropogenic (human-caused) changes. Take the natural changes: we know of ranges, rates of change and recurrence times, if imperfectly (orbital changes are well known, solar changes less so, volcanism poorly so). We also know something of the amplifying factors (e.g., ice albedo as an amplifier of radiative trapping) and of ultimate effects (e.g., oceanic temperatures), more imperfectly. Furthermore, we know that some anthropogenic changes lie outside the bounds of past natural changes — specifically, the rate of rise of atmospheric CO2, as well as deforestation rates that affect the absorption of solar radiation and the cycling of water (the part going through plants) in the atmosphere.

The potential for anthropogenic changes to exceed the bounds of natural changes is raised by the multiplicity of changes caused by humans, such as never have occurred in the earth’s history. Simultaneously, we are changing greenhouse gas concentrations, land cover, atmospheric aerosol concentrations (by burning biomass, especially), ozone concentrations at the surface and in the stratosphere, reactive nitrogen concentrations on land and in waters (e.g., fertilizer runoff in rivers leading to algal blooms and then dead zones in coastal waters), and so on.

We need to be prepared for both natural and anthropogenic changes, by acquiring knowledge about the changes and their effects. The imperfection of our knowledge about natural changes alone is daunting and it’s demanding of research ranging from understanding causes to preparing for effects. When we add in the imperfection of our knowledge about anthropogenic effects, the challenges are much greater. We certainly cannot reduce concerns about these with the idea that natural changes are occurring anyway.

Jim Bouldin, research ecologist at the University of California at Davis, adds:

Vince’s answer is great. I’ll add a couple points to it.

A lot could be said here. Although a given amount of radiative forcing will have the same temperature effect on the planet regardless of whether humans produced it or not, the primary human forcings (greenhouse gases and aerosols) have other effects that, for example, a change in solar irradiance, would not have. For example, CO2 acidifies water bodies and changes plant physiology in certain plant groups, and aerosols can cause human health problems, etc.

Peter Fray

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