New Zealand Institute of International Affairs
Department of Earth and Ocean Sciences
Questions and Answers on Climate Change
30 April at 1.10pm in Lecture Theatre ELT
A Seminar, and open question and answer session, prefaced by two ten minute
summaries of important aspects of the science of climate change. This is your
chance to have that question answered that you have so long pondered.
The speakers:
Professor Bob Carter, James Cook University, Queensland
THE GEOLOGICAL CONTEXT FOR CLIMATE CHANGE
The issue of dangerous human-caused global warming is mostly discussed in terms of contemporary
global average temperature change. This is unsatisfactory, because the 150-year-long record of
thermometer temperature measurements is trivially short, representing only 5 climate data points.
Climate change is as much a geological as it is a meteorological issue, for true climate change can only
be studied over periods of at least hundreds of thousands of years. From studying climate records over
the last several million years, palaeoclimatologists and palaeoceanographers have established a sound
understanding of the natural patterns and some of the mechanisms of climate change. The most
important evidence comes from sediment cores from beneath the deep seafloor and ice cores through
the Greenland and Antarctic ice caps. This evidence indicates that the phase of mild global warming that
terminated at the end of the 20th century falls well within known natural climate variability, and was not
unusual in either its rate or its magnitude.
Dr Willem de Lange, University of Waikato
OCEANIC INFLUENCES ON CLIMATE CHANGE
The oceans store and redistribute thermal energy (heat) on the surface of the Earth, and therefore play
an important role in regulating climate change. Ocean currents transport heat from the Equator to high
latitudes. The redistribution is not uniform, and in effect heat is transported from the North Pacific to
the North Atlantic. This is balanced by a net transport of water vapour (and heat) from the North
Atlantic to the North Pacific by the atmosphere. The movement of heat fluctuates at different time
scales. For example, the El Niño-Southern Oscillation involves fluctuations across the tropical Pacific
Ocean over 2-7 years. The Pacific Decadal and Atlantic Multidecadal Oscillations operate at 50-80 year
cycles. Geological evidence indicates that a strong 1500 y Bond Cycle is also important. Since the main
source of heat in the ocean is the Sun, it is likely that fluctuations in solar activity over periods of 1001500 years will also be significant. Analysis of sea level, sea surface temperatures, and ocean heat, show
that natural cycles have been dominant up until the present, and there is no compelling evidence of any
change to their behaviour.