Why climate change is a big deal – some perspective

First things first: the UN’s Intergovernmental Panel on Climate Change has just released its Fifth Assessment Report, and the picture is no rosier than it’s been for the first four. Here’s a quick graphical update on our current state of the art with respect to land and ocean temperatures:


In the graphs above, the blue bands indicate climate model predictions using just natural forcings on climate (e.g., solar radiation) while the red bands indicate predictions using natural and anthropogenic forcings (e.g., human burning of fossil fuels). The black lines show the observed data.  Every time you see a black line in a red band, that shows where a model including anthropogenic forcings on climate was a better fit to the data than was a model that did not include anthropogenic forcings. These data show the following:

1) The land has warmed, and as predicted by anthropogenic forcings.

2) The oceans have warmed, and as predicted by anthropogenic forcings.

3) Arctic sea ice is on the decline, and as predicted by anthropogenic forcings.

So climate change is real, and we’re causing it.


“Who cares?  The climate of this planet has never been stable. There used to be hippos wallowing above the Arctic Circle!”


True, for most of the history of life on earth, there was no ice at the poles at all.  If anything, a warming trend to pull us out of the current glacial period in which we’re living would move us toward a more typical condition of global climate.  That’s not the point, however.  The point is people.


Consider this very sad infographic summarizing the Syrian refugee crisis:


Within Syria, 6.5 million people have been displaced.  Another 2.5 million have fled the country to settle elsewhere.  Note that this is not called the “Syrian Refugee Holiday” or the “Syrian Refugee Picnic.” This is a crisis.  People die, societies break down, violence erupts, diseases break out – refugee crises breed economic and political instability, in addition to the miserable suffering felt by the individual refugees.


“Yes, the situation in Syria is bad, but it’s got nothing to do with climate change.”

Bear with me.

Consider now just one facet of climate change: rising sea level.


If anything, our observations of rising sea levels have exceeded earlier projections by the IPCC.  Sea level is more than just a function of melting glaciers.  It also rises as the water warms and undergoes thermal expansion:  warm water occupies more space than cold water. How high might sea level rise by 2100? Looks like 1–2 m is safe bet:


Sea level rise is about peopleWorld Ocean Review predicts that 13 million Europeans would be threatened by a 1-meter rise in sea level.  Our global population is over 7 billion, and climbing.  About 200 million people today live in low-lying areas prone to coastal flooding; that number is expected to increase to perhaps as much as 500 million by 2100.

This is Bangladesh, home to 150 million people, and almost all of them living in low-lying areas.


The dark reds on this map indicate areas extremely vulnerable to sea level rise – they are flood prone and support high population density.

If you forget about any of the other impacts of climate change, from food insecurity to water shortages to disease outbreaks to catastrophic fires, just focus on this one aspect: a global humanitarian crisis of refugees from coastal areas.  Picture tens of millions of Bangladeshis displaced from their homes and pouring into India or Myanmar/Burma.  Heck, by 2020, it is projected that more than 130 million people in the US will live in coastal counties. In the coming decades, millions will be displaced and few countries (if any) will escape without experiencing their own refugee crisis.


Earth will be fine as its climate warms and its oceans rise; we won’t be.



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