[intro] So why aren’t we doing anything to stop the biggest problem to face humanity?
[intro] It’ll take a movement of concerned people like us to ensure our leaders act in the face of the biggest challenge to ever confront humanity.
350 Climate Presentation Overview Intro Climate science (or, climate change is real) Climate impacts (or, climate change is happening now) Climate solutions (or, we know that solutions exist) Climate politics (or, so why aren’t we doing anything about it?) Conclusions
[science] we know climate change is real.
[science overview] What is climate change? What is causing it? How sure are we? Are we too late?
1 What is climate change?
What is climate change? Climate is the average weather conditions of a place or area (or the whole globe) over a period of years ‘Climate change’ is a long term change in the average weather
Our climate has always been variable. Glacial periods and warmer periods have occurred throughout Earth’s history. This variability is natural and is caused by many things
HOWEVER… Global temperature change (between glacial and interglacial periods) occurs normally at a rate of 0.05 – 0.005°C every 100yrs. In the last 50yrs the global average temperature has increased by 0.5 degrees! This is between 20 and 200 times the normal rate, and it’s accelerating!
We know the Earth is warming up quickly (figure 3)
Why is the Earth heating up? The Greenhouse Effect There are many greenhouse gases Carbon dioxide (CO2) – most abundant Methane Nitrous oxide CFCs Ozone The gases in the atmosphere that trap heat in the earth’s surface are called greenhouse gases and they occur naturally in our atmosphere, in small amounts. Figure from “The Wonders of the Weather” by Bob Crowder
Some greenhouse gases are good – they allow our planet to be warm enough to support life.
Scientists measure how our climate is changing in a few different ways
Ppm and Ppm-e
But historically, greenhouse gases have stayed in a particular range. Since industrialization, the concentration of CO2 in the atmosphere has risen from about 280ppm (parts per million) to over 392ppm due to human activities. The present CO2 concentration has not been exceeded during the past 420,000yrs and likely not in the past 20 million yrs (humans only appeared on earth 2 million yrs ago!) The earth’s fragile atmosphere, as seen from a shuttle
2 What is causing climate change?
Greenhouse gases are naturally stored on our planet- in plants and trees- below the ground as fossil fuels
But since the industrial revolution, human activity has caused these gases to be released at abnormal rates
That’s around the time when humans became dependent on coal and oil for transportation and energy.
The Carbon cycle Burning fossil fuels releases carbon into the atmosphere that has been stored for millennia (and otherwise would stay stored there)
There is no debate that burning fossil fuels releases greenhouse gases into our atmosphere – or that we have burned a lot of fossil fuels since the industrial revolution.
550ppm? More? Where we’ll be mid-century if we keep this up TODAY: 390ppm + Parts per Million CO2 EARLY 1900S CO2 in PPM LAST ICE AGE GLOBAL TEMPERATURE Years ago Throughout our history, global temperature has followed greenhouse gas concentrations
To recap: Humans are causing climate change. By burning more and more fossil fuels for our energy needs, it is very clear that: Humans have raised and continue to raise the concentration of greenhouse gases in our atmosphere When greenhouse gas concentrations rise, global temperature rises. We are observing that very rise in temperature to match the rise in greenhouse gases.
3 How sure are we of the science? Really, really sure on the general gist, but a little less sure on the specifics
The largest research project in history: In 1988, the IPCC was created to “provide the decision-makers and others interested in climate change with an objective source of information about climate change”
“Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities.” The US National Academy of Sciences, 2010
Number of scientific studies dealing with “climate change” published in scientific journals between 1993 and 2003: Number disagreeing with the global consensus that greenhouse gas pollution has caused most of the warming of the last 50 years: And anyone who tries to tell you differently needs to take a closer look Science, December 3, 2004 Vol. 306, Issue 5702,1686
There is uncertainty about just how our climate will change in the future That’s because our earth is such a big and complex system But in general, scientists’ predictions have tended to be conservative compared to observed impacts so far UNCERTAINTY
EXAMPLE: MELTING OF THE ARCTIC New predictions Satellite observations Mean IPCC prediction Most likely change (melt) IPCC range Actual observed melting % change in ice cover it has melted nearly80 YEARSahead of when scientists predicted YEAR
Much of the uncertainty is due to “feedback loops”, when climate impacts reinforce and amplify each other, which can be hard to model Example: The Albedo feedback loop Earth gets warmer, causing arctic ocean to warm White sea ice melts, exposing dark ocean underneath Dark ocean reflects less sunlight, absorbs more energy
4 So are we too late?
Once emitted, greenhouse gases stay in the atmosphere and trap heat for decades. That’s why its essential to cut emissions now. It will be difficult to stabilize our climate, but it’s not impossible.
Thankfully, we know where we need to aim: “If humanity wishes to preserve a planet similar to that on which civilization developed and towhich life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 387ppm to at most 350ppm.” - NASA climatologist Dr. James E. Hansen, 2008
The 350ppm target means that at our current level – 392ppm, we are already in the danger zone. The Earth and the species that live on it have never gone through a change in climate such as the one we are now facing. But it’s not too late – if we act now!
Up Next: Find out how climate change is already impacting our planet. Intro Climate science (or, climate change is real) Climate impacts (or, climate change is happening now) Climate solutions (or, we know that solutions exist) Climate politics (or, so why aren’t we doing anything about it?) Conclusions
Sources and more information Grist “Denier Argument FAQ” section 350.org “Science of 350” and “FAQ” sections “2 Degrees, One Chance” James Hansen’s “Blue Planet” Scripps CO2 Program Audubon society