Climate Change: no comprende
A few times during the past two weeks, I have both heard and read about people who, having fully accepted that human-activity-induced climate change is real, are embarrassed about their inability to explain it. Considering I am significantly less educated than pretty much all of those people, with no scientific credentials whatsoever, I can safely say I understand. Though continually endeavouring to increase my knowledge of the economic, sociological, political and philosophical dimensions of this issue, in regards to the science, my understanding is still… woefully rudimentary.
So. Here is, in plain terms, my understanding of:
- What climate change is;
- How scientists know it is happening;
- How we know our carbon emissions are contributing to it.
Hopefully in the months and years to come my understanding of the science will become more comprehensive, and I’ll be able to write about it without trepidation. But this is essentially where I’m starting from.
Like most people I defer to reputable scientific sources and the advice of those in the know to inform my decisions. The following is a “brain dump” of my consequent knowledge on this topic. I’ve gone back to the original websites/articles for specific numbers, but the rest is essentially my laymen understanding.
1. WHAT IS CLIMATE CHANGE?
The greenhouse effect.
The earth has a naturally occurring greenhouse effect. The Earth’s atmosphere contains ‘greenhouse gases’ – water vapour, methane, nitrous oxide, carbon dioxide (CO2) and other gases that a naturally present in it. These gases in a way ‘trap’ infra-red radiation from the Sun on the planet, which raises the temperature of the Earth’s surface and the lower atmosphere. This naturally occurring greenhouse effect is what has made the Earth so habitable for mankind.
The earth’s orbit around the Sun has had variations throughout history, which in turn has affected the amount of sunlight reaching the Earth’s surface and affected warm and cold periods naturally.
The unnatural greenhouse effect – human-induced climate change.
For some 200 years, beginning with the Industrial Revolution, humans (increasingly numerous and eager to consume) have been lofting unprecedented amounts of CO2 and other greenhouse gases into the atmosphere. More greenhouse gases in the atmosphere has intensified the greenhouse effect, and global temperatures have risen significantly in a relatively short period of time. In the past five years, an authoritative assessment of climate change undertaken by the world’s scientists concluded that this recent rise in global temperatures has been affected by human activities. This is what we call human-induced CLIMATE CHANGE (previously ‘global warming’).
CO2 levels in the atmosphere are now higher than they have been in the last 650,000 years, which is the period for which reliable data has been extracted from ice cores. Levels are expected to increase due to continuing burning of fossil fuels and human activity. Ten of the hottest years ever recorded were in the last 14 years.
The planet can handle increasingly higher surface and atmospheric temperatures… but increasingly higher temperatures and ensuing weird and intensifying weather patterns pose a threat to human survival on Earth – affecting already where we live, where we can live, our food and water supply, etc. The spread of tropical diseases to places previously too cold for such diseases is also a possible development. Another likely development: climate change refugees. Many islands are set to disappear under rising sea levels (caused by melting polar ice caps), including the islands of our neighbours in the Pacific. Given the low impact and humble lifestyles of such islanders, this would be yet another appalling injustice of indigenous people’s lives and livelihoods being adversely affected by the obese lifestyles of first world peoples.
But, I digress. That’s another post. Back to the science.
2. HOW DO SCIENTISTS KNOW IT’S HAPPENING?
Ok, this is what I know.
In 2009, the National Oceanic and Atmospheric Administration (NOAA) published the State of the Climate 2009 report. The reports contributors included over 300 scientists from 160 research groups in 48 countries.
Drawing from comprehensive data from multiple and diverse sources (eg. satellites, weather balloons, weather stations, ships, buoys and field surveys, etc) the report sets out 10 measurable global indicators of changing temperatures. The changes in those indicators are consistent with a warming world.
Seven of those indicators are rising:
- Air temperature over land.
- Sea surface temperature.
- Air temperature over oceans.
- Sea level.
- Ocean heat.
- Tropospheric temperature in the “active-weather” layer of the atmosphere closest to the Earth’s surface.
And three of those indicators are declining:
- Arctic sea ice.
- Spring snow cover in the Northern hemisphere.
Looking at air temperature and other climate indicators, variations year to year can be seen due to natural variability (eg. natural climatic variations such as El Niño/La Niña events). In order to understand climate change, the longer-term record had to be studied – the average temperatures decade-to-decade. And the long-term study points to increasing global temperatures. Each of the last three decades has been much warmer than the decade that preceded it. At the time, the 1980s was the hottest decade on record. In the 1990s, every year was warmer than the average of the previous decade. Similarly, the 2000s were warmer too.