Climate futures for Central Otago and the

underlying scienceGreg Bodeker

Presented at the Community Climate Change Discussion Forum

Alexandra Community Hall, 7 November 2015

Globally averaged combined land and ocean surface temperatures: 1850 - 2012 Three different

data sets.Each of the last 3 decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.In the Northern Hemisphere, 1983-2012 was likely the warmest 30-year period of the last 1400 years (medium confidence).

But maybe it’s all just natural cycles

observations

But models are really just another form of witchcraft right?

GCMGlobal Climate Model

On each grid point: Temp, moisture, wind, pressure“Sub grid-scale” processes are “parameterised”: clouds, vegetation, surface heat exchange,…Discretizes the equations for fluid motion and integrates these forward in time.Contains parameterizations for processes on smaller scales.Used in IPCC 5th assessment report.

Climate Models

Tell me a storyStatement made by the IPCC 5th assessment report:

Earth in 2100 is likely to be between 0.3 and 4.8°C warmer than it was in the late 20th

century.Good grief that’s an awfully uncertain result. If it’s 0.3°C do we really have to worry?The uncertainty is not the result of uncertainties in the models or in our knowledge of the climate system. It is the result of our uncertainty in humans. The rise in temperature depends largely on what we choose to do now – where our energy and food come from, the type of buildings we live in and the cars we drive. Essentially we have three choices:

1) Adapt 2) Mitigate 3) Suffer

http://futureextremes.ccii.org.nz/

Thanks to Jared Lewis for making

this a reality

Climate change where we are

The results

Significantly more days with daily maximum temperatures going above 25°C and way more days with daily maximum temperatures going above 30°C.

Daily minimum temperatures for Alexandra

Fewer frosts. Less complaining from the kids when they have to walk to school.

What about rainfall?

No clearly discernible change in rainfall in Alexandra, but we should also consider rainfall changes in the Clutha catchment.

What about the rest of New Zealand?

Number of days with Tmax>25°C in 2015

Number of days with Tmax>25°C in 2100 under RCP8.5