Global temperatures are rising at unprecedented rates along with increases in CO2 in the atmosphere and oceans. Last year (2016) was the hottest since record keeping began. Both phenomena are a result of human economic activities, including fossil fuel burning, the intensification of agriculture, and other forms of land degradation. These trends lead directly to a host of climate change effects, most of which are destructive to the natural world and disruptive of human life.
The build-up of heat in the atmosphere and oceans, both from increased trapping by greenhouse gases (water vapor, CO2, methane, nitrous oxides, halocarbons) and especially from increased heat radiation off of land surfaces, has globally catastrophic long-term consequences for humanity as sea levels rise. Some of those effects are beginning to manifest at threatening levels. However, of even more immediate concern, global warming is kicking the climate system into overdrive and producing more and more extreme weather events of flood, drought, fire, and storm. These in turn are causing dramatic and widespread economic losses and societal disruptions that have the potential to provoke the collapse of whole nations.
The climate system is a complex set of global and regional feedback loops and forcing mechanisms driven by orbital physics, tectonic, biological, atmospheric, and weathering effects. While seen against the backdrop of geologic time, Earth is now in an “Icebox” phase, the past 10,000 years have been a relatively mild and warm period, known as an interglacial - between ice ages - during which all of human history has emerged. From about 7,000 years ago, humans entered the climate equation as early deforestation for farming appears to have deflected a long-term cooling trend, while the application of machinery to farming, the industrial era, and fossil fuel consumption beginning about 1850 led to the current spike in global temperatures. Our signature is written all over the climate change now underway.
While human influence on the climate began with farming, the changes since 1850, and particularly since the end of WWII, have been decisive. Two global trends converge during the last 70 years: a dramatically increased use of fossil fuels for all economic purposes, and a de-greening and de-forestation of the planet, primarily from the expansion and intensification of agriculture, but also from urbanization. Both have driven and been driven by a huge increase in human population, from about 2 billion to more than 7 billion. The second trend is inextricable from the first. Fossil fuels, while contributing excess CO2 to the atmosphere, have enabled humanity to convert green biosystems into semi-deserts by industrializing agriculture and clearing and paving over large areas for human settlement. That has reduced nature’s ability to absorb the CO2 being released by ever-more numerous smokestacks and tailpipes.
Of importance to policy makers and society at large are three things:
1. Thoughtless and ignorant human activities have provoked unprecedented warming;
2. Extreme weather events driven by global warming are already disrupting communities with grave consequences should these trends continue; and
3. The climate system itself has momentum that makes mitigating action urgent within the next decade.
The change of scale from humanity’s infancy 10,000 years ago, to its out-of-control rampage against nature occurred in a short period. Feedback was delayed by the vast size of the climate system, an historically mistaken sense of our impacts, ignorance of the complexity and responsiveness of planetary systems, and self-serving ideologies. We have just begun to learn the lessons of climate change, and have further to go before we can adjust our behavior. Unfortunately, because of earlier delays and the momentum of the system, urgent action is now required.
The frequency of billion-dollar losses due to storm damage has risen steadily throughout the 21st century. These large numbers mask the reality of human tragedy as millions are displaced, homes and infrastructure are destroyed, and thousands of lives are lost—each year. Flooding was widespread throughout the U.K. for months in 2013-14, exceeding record levels set in 2007 and 2000. Budget-cutting by the climate-skeptical Conservative government that targeted coastal defences was blamed for increasing the damage, as $3 billion was lost from a notional saving of $500 million. Baton Rouge, Louisiana received over 30” of rain in August 2016, driving tens of thousands from their homes, and damaging 146,000 houses and thousands of businesses, churches, schools, and public buildings.
Heatwaves have begun to shatter nations and whole regions. Drought and failure of the farm sector set the conditions leading to the 6-year Syrian civil war, destroying that country and destabilizing its neighbors. In May 2010, Pakistan experienced all-Asia, all-time record temperatures of 129°F in a 9-day heat wave, and two months later the worst-ever nationwide flooding, as nearly two million homes were destroyed. Russian grain exports were halted when heat (111°F) and fires (500,000 acres) in 2010 suppressed the harvest. Smoke blanketed the huge nation and more than 56,000 died of air pollution-related causes. Radioactive lands near Chernobyl were ignited, threatening to spread radionuclides widely. The grain export ban is thought to have bred food shortages that helped trigger the Arab Spring rebellions.
Sixteen of the 18 hottest years on record have occurred in this short century. Over 70,000 people died of heat-related causes in Europe in August 2003 as temperatures soared over 100°F. Chile is presently being overwhelmed by forest fires, not unlike those that have recently raged through the American West. Wildfires burnt almost 120,000 acres in the Southeast this past autumn, including over 700 buildings near Gatlinburg, Tennessee after drought in the summer prepared the way. The Northeast is now in drought, and despite recent flooding, California remains stubbornly below normal levels of moisture, threatening the nation’s most valuable agricultural economy. Fires in Oregon throughout the summer of 2016 made outdoor activity hazardous. Brazil’s largest city, Sao Paolo, home to 20 million, virtually ran out of water in 2015. Ft. MacMurray, Alberta, a city of 88,000, was evacuated last May in the face of massive wildfires.
These conditions are not normal, and even where studies indicate that similar extremes have occurred in the past, such as 10-year droughts in the Southeast, our modern societies are unprepared for their impacts.
Ice core data, pollen records, and even historical accounts show that the climate can switch directions abruptly, and that despite its apparent robustness, may be vulnerable to rapid change from forcing or positive feedback loops such as methane releases from melting permafrost, Arctic warming due to reduced snow and sea ice cover (lower albedo), and loss of vegetative cover in semi-arid regions.
In addition, the oceans are absorbing large amounts of carbon dioxide and much of the heat load imposed by human activity. At some point which we cannot predict, but which could be soon, this will reverse and the curve of heating may accelerate further.
The immediate dangers of climate change are increasing extremes of flood, drought, fire, and storm. A warmer atmosphere holds more water vapor, increasing the risk of intense rain and snow events. Warmer oceans generate larger hurricanes and typhoons. Disruptions of oceanic currents and the jet stream from Arctic warming have thrown off familiar patterns of rainfall and seasonal temperature, reducing food production. Added heat in the tropical Pacific is increasing the frequency of El Niño events with world-wide effects that include severe drought, high temperatures, and weakening of the Indian and east Asian monsoons.
A full litany of disasters would require dozens of pages to present, but we should reflect on the scale of recent impacts lest we lose perspective: two storms, Hurricanes Katrina and Sandy, cost the U.S. more than $175 billion, over 1% of annual GDP, and claimed more than a thousand lives in New Orleans, New York City, and their surrounding regions. These were fully modern and wealthy cities, both critical to the national economy, but their influence did not spare them. Neither has fully remediated the damage. Both calamities led to permanent out-migration. With already weak underlying economic conditions, it is easy to foresee how the curves of mounting climate disaster and faltering economic growth will cross and fatally undermine our ability to recover.
Climate scientists have focused for the past 40 years on the growing load of greenhouse gases in the atmosphere, and the world’s efforts to address the crisis have, heretofore ineffectively, attempted to limit their annual increase. Because of lag effects, momentum in the climate, and vast amounts of CO2 stored in the oceans, even a complete cessation of industrial and agricultural carbon emissions today would not result in turning down the world’s greenhouse gas levels or temperatures for at least 30 years. Given the impacts we are already experiencing, we cannot afford to rely only on this important but wholely inadequate mechanism.
About half the carbon emissions from human activity are presently absorbed by forests, soils, and the sea, but human demands on the biosphere continue to erode their restorative capacity. If we are to cool the planet in time to mitigate a growing environmental catastrophe, we must greatly amplify the ability of green nature to rebalance the Earth’s heat budget.
Greenhouse gas trapping accounts for only about a quarter of the heat dynamics of the atmosphere. Of the greenhouse gases impacts, carbon dioxide represents about one-fifth, other industrial gases another fifth, and water vapor at three-fifths the greatest portion. Other effects, mostly related to the water cycle, dominate surface and atmospheric heating and cooling. Human actions have changed this balance detrimentally and we can change it back.
Land clearance for agriculture and development has reduced forest cover, while industrial forestry has degraded forest age and density. Mechanization and chemical fertilizers have reduced the seasonal length of green cover on farmland by enabling broadscale clear cultivation and by supplanting crop rotations. Tillage and chemical use have dramatically reduced soil carbon content, and with it the ability of landscapes to hold, and thus to cycle water to the atmosphere. When bare of plant cover, soil temperatures under sunshine can spike from a normal 68° to over 140°F. Radiation from a dark surface is proportional to the 4th power of the temperature difference, so these effects are huge. Radiation from urban pavements is the most evident demonstration of these physical laws, but naked farm fields reproduce the same brutal conditions on a massive scale.
The churning of billions of tires on roads, the plowing of billions of acres, increasing wildfires, and the hubbub of humanity along with our industrial pollution release immense swaths of dusts, smoke, and hazes into the atmosphere where they contribute to capturing heat from sunlight and preventing its release from the Earth’s surface to space. Hazy night skies are particularly damaging to the planet’s ability to cool itself, and their incidence is widespread and increasing. While these haze particles and droplets of moisture can aggregate into rain and snow, to do so, they must nucleate around either salts, ice crystals, or bacteria. Salts dominate over the oceans, ice crystals in polar regions, and elsewhere — most of the inhabited regions of the planet — aerobacter, produced chiefly in the stomata of tree leaves, make the rain and snow.
As raindrops and snowflakes form in the atmosphere, millions of dust and haze droplets coalesce, clouds amass, and as they do, naturally reflect incoming sunlight high in the atmosphere, preventing it from heating the surface. When saturation occurs, the clouds release moisture to the ground and further cooling occurs. With subsequent clearing of the air, often at night, yet more heat can radiate to the top of the atmosphere and out to space, leaving the Earth system. All these processes are natural and ongoing, but heating and cooling effects, which have been regulated by biosystems for millions of years, are out of balance due to thoughtless human impacts.
To restore the Earth’s ability to cool itself naturally and safely, we must increase the water-holding capacity of our landscapes, first by a wide array of micro-engineering works, and in the longer term by returning organic matter (carbon) in soils to levels that prevailed before plow agriculture. Although this will move carbon from the atmosphere into stable storage in plants and soils, it is the thermodynamic effects of water that can make the quickest impact on global temperatures and weather extremes.
Transpiration and evaporation from vegetated surfaces (called latent heat) releases a quarter of the incoming solar radiation without raising temperatures. Extending the length and expanse of green cover on land is the most powerful way we can aid the planet to cool itself.
As part of this strategy, we must replant, restore, and preserve forests, and do so in a way that ensures continuous forest cover from the oceans toward continental interiors. Studies have shown not only that forests draw in moisture from the surrounding atmosphere — making it available as regional rainfall — but that they are essential in transpiring and transferring rain from moist coasts to otherwise dry interior regions.
Our farmers must be supported to reduce chemical use and eliminate most tillage so that farm soils can recover their carbon content. This will entail the greater use of cover crops and the introduction of well-tested agroforestry systems. Grazing practices mimicking predator pressures can greatly enhance carbon uptake in pastures and on rangeland. Wetlands and riparian woodlands must be restored along all streams. Green roofs, porous pavements, rain gardens, and other green infrastructure must come to dominate our urban landscapes with the aim of dramatically reducing runoff to waterways.
Of course efforts must continue to reduce the use of fossil fuels, to de-link economic value from energy consumption, and to make these processes equitable across society, but even more urgent, if we are to avoid crushing burdens from extreme weather events, is to initiate massive programs for land repair, reforestation, water harvesting, and to transform our agriculture to capture carbon. The effects of these efforts will be felt first regionally — so states, provinces, cities, farm communities, and even individuals can take leadership — but they will impact the global situation. The promise of restored biosystems is a more temperate climate, more comfortable and gracious towns and cities, increased employment, a more profitable and productive agriculture, and lower levels of violence, stress, and trauma across society. The alternative is virtually unthinkable.