According to a new study just published in the journal Geophysical Research Letters, the global climate would be about 3 deg C colder than present were it not for man-made carbon dioxide and methane emissions.
If this is correct then in the absence of Anthropogenic Global Warming we would have been experiencing conditions like that seen in the Little Ice Age in the 17th century. No doubt many scientists will look at this latest research and take issue with it, but just consider the implications if it were true.
How would modern civilisation have coped with Little Ice Age conditions? I dealt with the situation in my book, “The Sun: A Biography.”
“In the 17th century many French villages recorded the date at which the local grapes became ready to harvest. They show that, starting in the mid-century, they ripened one or two weeks later than before. Cereal production also slumped in the mid-seventeenth century. Starvation was widespread.
Everyone in Europe and possibly beyond felt the cold and knew in the back of their minds that things were worse than they were a generation or two previously. Tidal rivers like the Thames froze over for long periods in the winter allowing the famous Frost Fairs. Travellers in Scotland said that the main peaks of the Grampians and Cairngorms retained their snow all year. Surges of cold water southward from the polar regions ruined the cod industry off Iceland. As the fishes kidney reacts badly to water colder than 2 degrees C there was no cod between 1675 – 1750. In 1695 it was reported that an Inuit was found in his kayak in the river Don in Aberdeen. The same year the canals of Venice froze in the winter. The English preacher John King wrote, “our years are turned upside down, our summers are no summers; our harvests, no harvests.”
The Little Ice Age affected Europe at just the wrong time. In response to the more benign climate of the Medieval Warm Period, Europe’s population may have doubled. More people married, and most did so earlier giving birth to six or seven children despite, or perhaps because of infant mortality being high. But in the mid-seventeenth century demographic growth stopped and in some areas fell, in part due to the reduced crop yields. Bread prices doubled and then quintupled. Buying bread absorbed almost all a family’s income, in turn, causing the demand for manufactured goods to collapse and resulted in unemployment.
High prices and reduced incomes forced many couples in Europe to marry later and the average age of brides rose from teenagers in the later sixteenth century to twenty-seven or twenty-eight in the mid-seventeenth reducing the birth rate. Hunger weakened the population. The English philosopher Thomas Hobbes argued in 1651 that `the life of man [is] solitary, poor, nasty, brutish, and short’. “
The new study is by the University of Wisconsin-Madison’s Gwenaëlle Philippon-Berthier, Stephen Vavrus, and John Kutzbach, along with University of Virginia’s William Ruddiman. They used a standard climate model to examine what the earth’s climate and vegetation may have been like in the absence of any human greenhouse gas emissions.
They concluded; “…based on the GHG levels inferred from previous interglacials… we estimate that in the absence of all anthropogenic GHG emissions, the current climate would be approximately 3.14 deg C cooler. We find that a substantial amount of this climate change (nearly 0.5 deg C) is attributable to vegetation feedbacks.”
It thus seems possible that without GHG emissions our global climate would not be able to support us in the population it does today.
The researchers estimate that because of the colder and drier conditions, along with lower levels of atmospheric carbon dioxide, global photosynthesis output would decline by 39%, and leaf area would be reduced by 30%.
In the Northern Hemisphere mid-latitudes, forest cover would be 60% less than it currently is and grassland area would be 17% less. In the high latitudes, the area of boreal forests would fall by 69% while the polar wilderness would increase by 286%. In the Tropics the effects would not be so dramatic but still devastating for the population, grass area would decrease by 3%, forest area by 15%, and the area of bare ground would increase by 344%.
So, whatever the pottential scenarios for the future, it is possible mankind’s GHG emissions may have produced a warmer, greener planet, supporting more people, that it would otherwise have been.