The crux of Dr Stephen Pekar’s presentation first thing yesterday was this: there is no debate among scientists about the authenticity of climate change and whether human activity is causing it. The challenge, he said, appears to be how to effectively communicate this fact to policy makers and a public that continues to mistakenly perceive that there is debate among scientists.
Dr Steve is a geology professor. He presented some of the findings of his research into past climate and oceanographic changes during times (16 to 45 million years ago) when CO2 was as high as what is predicted for the end of this century (anywhere from 500 to 900 parts per million).
He talked about the causes of climate change, splitting them into the natural causes—changes in solar output, ocean movements, volcanoes etc; and human causes—increased trace gases in the atmosphere, land use change, aerosols.
He talked about the utterly compelling record of climate change we have since 1880 of temperatures increasing since then, especially in the last 20 years. (When scientists say a record is compelling, it means they and all their colleagues have tested and interrogated the record over and over and over and over and tried to prove it wrong from every single angle. So scientists say ‘compelling’ when the rest of us would say ‘it’s like totally true’.)
But 100 years is pretty short in the life of the earth. Hell, it’s short in the life of humanity or even a single culture. So Dr Steve started in on the old old old stats. He’s a geologist after all; that’s what he does: drills into ocean beds and prehistoric ice to find out what happened long times ago.
I found out that during the bit-more-than-a-millennium from 900 CE to now, there has been some fluctuation in global temperatures. For example, in medieval times there was a warm period. It was nowhere near as warm as it has been since the 1880s when the industrialisation of everything saw a massive spike in global temperature which has been increasing ever since. Although the medieval warm spell was nothing compared to the projections for 2099 which predict anything from an increase of 2°C to 6°C.
The oldest ice core we have is from 800,000 years ago. Analysing it has revealed that atmospheric CO2 has been under 300 parts per million since then. Current projections for the end of this century are between 500 and 900 ppm.
The upshot of all this is that, over the last couple of centuries, human activity has been changing the climate more than it has changed for tens of millions of years. The last time something this dramatic happened was when that asteroid hit the earth and killed all the dinosaurs. The changes we have seen over the last century or two usually take hundreds of thousands of years.
A few facts from Dr Steve:
- 1-1.5°C warming would be a similar climate as 6000 years ago. That’s normal climate change.
- 2-2.5°C warmer than now happened 125,000 years ago. Back then sea level was 6 m higher than now.
(These last two kinds of changes due to slight changes in earth’s orbit and other cycles.)
The last time CO2 may have affected climate was 3 to 5 million years ago when it was about 400 ppm. The last time CO2 was as high as predicted for 100 years from now was 7 million years ago.
Today the world is pretty icy because we are in one of the coolest time periods in the last 100 million years. This is what we’re used to. We have been in this climate since humans have been humans. All homo sapiens have lived in this cooler drier period. It’s only during the last 5,000 years, we’ve built cities and started with the whole agriculture/intensive food production thing. We’re not mobile like we were when we could just swing to higher tree.
When the earth was at its warmest, the sea was at least 70 m higher than it is now. A rise of 1 or 2 m will cause destruction and disaster to places like Bangladesh. Imagine what will happen when the planet heats up enough for the 6 or 7 m that scientists agree is most likely.
Collecting the data that allows us to make all these predictions with enough certainty that scientists feel comfortable saying ‘likely’ has taken hundred of painstaking missions to drill deep into ocean beds and prehistoric ice sheets. In each drill core, every 2 cm represents 100,000 years. That little tidbit of info kind of blows my mind.
One of the most successful marine based organisations in work that increases our understanding of the earth is the Integrated Ocean Drilling Program (IODP). Australia is an associate partner of the non-profit and it has drilled at hundreds of places around the world in deep ocean beds. IODP’s aims are to find out:
- what is natural or normal
- how fast sea level can rise
- about the earth’s record of variability
- how sensitive the climate is
- how the ocean is different under conditions of high CO2
- how much gas hydrate there is in the earth (most of it is frozen methane on the bottom of the ocean)
Incidentally, methane is 20 times more effective as a greenhouse gas than CO2 and there’s lots in the ice sheets. If/when they melt, the methane would be released into the atmosphere. The last time that happened, the temperature of the arctic ocean was 23°C. Hello Water World.
Another project is the Andrill program in Antarctica. Andrill investigates Antarctica’s role in the global environmental change in the Cenozoic Era. Dr Steve spent a season working there. One of the things the project has found out is that coral reefs didn’t exist when the earth was that hot. So they’re going to die if/when we warm up to those levels again.
So basically, here’s the rub: climate change is real. We’re causing it. We are working out how to deal with it.
You can see all my Tipping Point posts under the Tipping Point tag.