Hotter sooner faster: Global temperature changes over the past 136 years

Graph of global temperature anomaly from 1880 to 2016
Global temperature anomaly, 1880 to present

This graph shows the global temperature anomaly: how current temperatures compare to latter-twentieth-century “normal” temperatures. Normal, here, is the 1951-1980 average.

in looking at the global temperature data, three things are apparent. First, the Earth is already warming. The graph has been trending strongly upward since at least the 1980s. Second, the increase in temperature from the 1951-1980 baseline period will soon reach one degree Celsius. Indeed, temperature outliers such as those in February and March 2016 are approaching 1.5 degrees. Temperatures are rising fast—charting significant increases in decades, not centuries. Third, there is in the data-points a suggestion that the curve may be getting steeper; temperature increases may be accelerating. It’s too early to tell, but given that global temperature increases are lagging well behind atmospheric greenhouse gas (GHG) increases, and given that global emission rates continue to increase, it is prudent to consider that temperature increases may accelerate beyond already-rapid rates.

How high might temperatures go? Here’s what we know. In the lead-up to the 2015 Paris climate talks, nearly every nation submitted to the United Nations a commitment to reduce GHG emissions. The United States committed to reduce its emissions by 26 to 28 percent (below 2005 levels) by 2025. Canada committed to reduce emissions by 30 percent by 2030. Other nations made comparable commitments. But the climate models show that even if every nation meets its emission-reduction commitments, our Earth will warm this century by 3.2 degrees Celsius—well beyond the so-called “dangerous” level of 2 degrees C, and more than double the 1.5 degree mark discussed in Paris. Indeed, the graph above makes it clear that 1.5 degrees was always pure fiction. In order to avoid a temperature increase of 3.2 degrees, we must set and meet more ambitious targets.

Climate science can be complicated. But at a public policy level—at the levels of citizens and legislators and democratic governance—climate change is simple and clear. It is happening. It is happening fast. And it will devastate our cities, economies, food systems, ecosystems, and perhaps even our civilization unless we act fast. Simple.

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Graph sources: Combined Land-Surface Air and Sea-Surface Water Temperature Anomalies from National Aeronautics and Space Administration (NASA) Goddard Institute for Space Studies (GISS): GISS Surface Temperature Analysis (GISTEMP).

It’s gonna get hot: Atmospheric carbon dioxide over the past 800,000 years

Graph of atmospheric carbon dioxide levels for the past 800,000 years
Atmospheric carbon dioxide concentrations, 800,000 years ago to present

There are lots of graphs related to climate change. Only a few, however, get to the core of the issue. This is one such graph. It shows atmospheric carbon dioxide (CO2) levels over the past 800,000 years—a period four times longer than our species, Homo sapiens, has walked the Earth. The units, parts per million (ppm), will not be familiar to everyone. But the units aren’t important. What is important is the shape of the graph, and the magnitude of current CO2 levels relative to those in the past.

As the graph shows, over the past 800,000 years, atmospheric carbon dioxide levels have risen and fallen. Low concentrations correspond to ice ages—eight such periods are visible in the graph. Higher CO2 levels correspond to largely ice-free “interglacial” periods. The critical point is this: in the 800,000 years before the modern era, CO2 levels never once rose above 300 ppm. Not once. Now, however, CO2 levels are 405 ppm. And because our emissions continue, it is likely that atmospheric concentrations will increase past 500 ppm, maybe past 600 ppm. Temperature increases are lagging behind CO2 increases. As Earth’s temperatures rise to “catch up” with the rapid increase in CO2, it’s going to get very hot. And it is going to stay hot for a long time.

There can be no doubt: humans are the cause of the rapid rise in CO2 levels. No one can look at the graph above and come to any other conclusion. The years 1800 and 1900 are highlighted. The fossil-fuelled industrial and transportation revolutions of the 19th, 20th, and 21st centuries are clearly visible in the graph’s vertical spike—an increase in atmospheric CO2 that has proceeded further and faster than at any other time in the past 800,000 years.

CO2 levels have increased by 100 ppm in a century. The data shows that such an increase usually takes 10,000 years. Humans are causing CO2 levels to rise 100 times faster than those levels rose at any time in the past 800 millennia. Even worse, the rate of increase is accelerating; at current and projected emission rates, the next increase of 100 ppm may take just 40 to 60 years.

It is impossible to overstate the danger of what we are doing. Words cannot convey how damaging continued CO2-level increases will be to the long-term prospects for human cities, societies, and economies, or to other species and the natural ecosystems we all rely upon. It is as if we have decided to set fire to our home, the Earth. Unless we extinguish that fire, all we hold dear will perish. Currently, we are pouring on gasoline.

Note: CO2 measurements for recent decades come directly from air samples. Measurements for past centuries come from analysis of air trapped in bubbles in Antarctic ice. Each ice core is analyzed at multiple research facilities using multiple techniques. Because of this duplicate testing and diversity of sampling methods, there is high confidence among scientists that ice-core data accurately reflects CO2 levels in previous centuries.

Graph sources:
– 800,000 years ago to 1913: Ice core samples, Dome C, Antarctica (Monnin et al. 2001; Siegenthaler et al. 2005; Luethi et al.) and Vostok, Antarctica (Petit et al. 1999; Pepin et al. 2001; Raynaud et al. 2005)
– 1832 – 1978: Ice core samples, Law Dome, Antarctica
– 1959 – 2013: Direct atmospheric measurements, Mauna Loa Observatory, National Oceanic and Atmospheric Administration (NOAA)

Too much tourism: Global air travel and climate change

Graph of global air travel, in trillions of passenger-kilometres, historic, from 1936 to 2016
Global air travel, trillions of passenger-kilometres per year, 1936-2016

The graph above shows that global air travel is increasing exponentially. In 2016, business travelers, tourists, and others traveled more than 7 trillion passenger-kilometres by air.  As you might expect, a passenger-kilometre is equal to moving one person one kilometre. Therefore, if a plane carrying 100 people flies 1,000 kms that is equal to 100,000 passenger-kilometres (pkms).

The graph’s shape is significant; it reflects exponential growth: an ever-steeper upward curve. A system that grows exponentially doubles in a constant time-period. The amount of air travel we consume is doubling every 15 years. Thus, over the past 30 years, it has doubled twice, such that pkms were more than 4 times higher in 2016 than in 1986.

This exponential increase—this doubling and redoubling—is predicted to continue.  Aircraft manufacturer Airbus projects that pkms will double again by 2030 and continue upward (Global Market Forecast 2016). Forecasts by airline industry group International Air Transport Association and Boeing similarly project a doubling in coming years.

This projected doubling by 2030 is significant and troubling. In the lead-up to the 2015 Paris climate talks, nearly every nation pledged to reduce greenhouse gas (GHG) emissions. Canada committed to reducing its emissions by 30 percent by 2030. The United States made a similar commitment: a 26 to 28 percent reduction by 2025. One could sum up the world’s commitments, roughly, by saying we have a global goal of reducing emissions by 30 percent by 2030. Over that same period, however, Boeing, Airbus, and the world’s airlines will be working to increase global air travel by 100 percent. Something has to give. If the world’s airplane manufacturers, airlines, resort destinations, and tourist industry succeed in redoubling air travel, the resulting GHG emissions will contribute to massively destabilizing Earth’s climate.

To meet our targets to cut GHG emissions by 30 percent in just 13 years, and by perhaps 50 percent or more by mid-century, we must ground most of the airplanes and replace them with trains powered by electricity generated from renewable, low-emission sources. If a traveler must cross the ocean, then perhaps that person should travel in a plane. But within the North American continent, within Europe, within Asia, and wherever oceans do not present a barrier, travel will have to be transferred over to fast trains. And because these trains can go from city-centre to city-centre, because trains can travel at hundreds of kms per hour, and because train journeys do not require the lengthy security checks common at airports, door-to-door travel times in trains can be less than those in planes.

Citizens and travelers face a choice: keep the planes flying, continue to increase the amount we fly, increase road travel similarly, miss our emission targets by a mile, and destroy our chances of a stable, prosperous future; or invest in high-speed rail, create local jobs, and create a twenty-first century transportation system that aligns with our emission-reduction and sustainability goals.  We must ground most of the global airline fleet if we want to meet our emission-reduction goals.  And we must build a new system of fast trains if we want to meet our travel and quality-of-life goals.  Indeed, there is no reason that the factories and technologies currently in possession of aircraft makers Boeing, Airbus, Bombardier, Embraer, and other manufactures could not be repurposed to build those trains.

Graph sources: Airlines for America: Annual Results World Airlines