Climate variability

Climate variability is the amount of change in climate that, all things being equal, we would expect to see. 

Much as we like to live in a stable and predictable world, nature is not like that. It changes all the time. Watch any parcel of nature long enough and it will shift around. Plants will grow, wither and die. New ones will take their place. 

Winter chills or long dry spells will see nature slow down and rest only to spring back to life when the rain falls.

Soil will move slowly down slope and occasionally fast if the profile is saturated and a storm front passes.

The challenge is to understand how much change is normal and so provide a reference sufficient to detect when certain events are genuinely unusual. This is difficult with climate because climate is made up of pattern — the predictability of the weather.

Climate variability is inevitable because the drivers of global warming and global cooling have been present throughout evolutionary time. The balance of energy in the atmosphere and oceans changes especially in relation the energy output of the sun and the fact that the earth wobbles in space.

The main drivers of climate change are 

• sun's energy output

• distance between the earth and the sun

• reflectivity of the Earth's surface [albedo]

• properties of the atmosphere to absorb and reflect the sun’s energy [the greenhouse gas emissions issues]

• properties of the landscape to absorb and reflect the sun’s energy [a less commonly mentions consequence of land clearing and urbanisation]

And as climate-change-wisdom explains, climate change is one of the main reasons we are here to be concerned about it.

Global temperature records

It is hard to get a handle on climate variability. 

In the decade from 2000 to 2010 before any mitigation actions kicked in, human activities released almost 100 billion tonnes of carbon into the atmosphere — considerably more than the normal flux and about a quarter of all man-made emissions since the start of the industrial revolution.

When global climate models factor this in they predict that surface temperatures should rise. Except that the 5-year average global surface temperature has been flat since 2005. And if it stays flat will soon fall outside the low-end predictions of the global models.  

It will be cooler than predicted.

This unexpected climate variation could be because there is a lag between greenhouses gas emissions and the impact on temperature and some warming will happen soon.

It could also be that warming has happened given there was a rise of more than 0.5 degrees from the late 1980’s to 2000 [a big change for a global average].

Or it could be that the effects of greenhouse gas concentrations in the atmosphere are not as predictable as the modelers would like.

Pragmatology of climate variability

Whatever the cause, the inability to predict climate variability with satisfactory precision is at the heart of the climate change conundrum

If we do not understand enough to predict the trend it is very hard to justify actions designed to alleviate it. 

All we can do is say that precautions are always wise. But no one made anything happen in his or her lives by being cautious. We are built for risk taking, courage and resourcefulness — caution is just the counterbalance to our innate need for action.

This explains why the only real global action on climate change has been through emission reduction policy, an action oriented response. It also explains why the naysayers are still so vocal. 

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