The State of Earth's Terrestrial Biosphere: How is it Responding to Rising Atmospheric CO2 and Warmer Temperatures?
Executive Summary
One of the potential consequences of the historical and ongoing rise in the air's CO2 content is global warming, which phenomenon has further been postulated to produce all sorts of other undesirable consequences. The United Nations' Intergovernmental Panel on Climate Change, for example, contends that current levels of temperature and changing precipitation patterns (which they believe are mostly driven by the modern rise in atmospheric CO2) are beginning to stress Earth's natural and agro-ecosystems now by reducing plant growth and development. And looking to the future, they claim that unless drastic steps are taken to reduce the ongoing rise in the air's CO2 content (e.g., scaling back on the use of fossil fuels that, when consumed, produce CO2), the situation will only get worse - that crops will fail, food shortages will become commonplace, and many species of plants (and the animals that depend on them for food) will be driven to extinction.
Such concerns, however, are not justified. In the ensuing report we present a meta-analysis of the peer-reviewed scientific literature, examining how the productivities of Earth's plants have responded to the 20th and now 21st century rise in global temperature and atmospheric CO2, a rise that climate alarmists claim is unprecedented over thousands of years (temperature) to millions of years (CO2 concentration). Based on that analysis, we find the following:
| - Satellite-based analyses of net terrestrial primary productivity (NPP) reveal an increase of around 6-13% since the 1980s. |
| - Earth's land surfaces were a net source of CO2-carbon to the atmosphere until about 1940. From 1940 onward, however, the terrestrial biosphere has become, in the mean, an increasingly greater sink for CO2-carbon. - Over the past 50 years, for example, global carbon uptake has doubled from 2.4 ± 0.8 billion tons in 1960 to 5.0 ± 0.9 billion tons in 2010 (see figure below). |
Annual global net carbon (C) uptake by Earth's lands and oceans (solid blue line) from 1959-2010, adapted from Ballantyne et al. (2012). The linear trend (dashed red line) and 1σ (dark shaded bands) and 2σ (light shaded bands) uncertainties are also shown.
3. The observed global greening has occurred in spite of all the many real and imagined assaults on Earth's vegetation that have occurred over the past several decades, including wildfires, disease, pest outbreaks, deforestation, and climatic changes in temperature and precipitation, more than compensating for any of the negative effects these phenomena may have had on the global biosphere.
4. There is compelling evidence that the atmosphere's rising CO2 content - which alarmists consider to be the chief culprit behind all of their concerns about the future of the biosphere (via the indirect threats they claim it poses as a result of CO2-induced climate change) - is most likely the primary cause of the observed greening trends.
5. In the future, Earth's plants should be able to successfully adjust their physiology to accommodate a warming of the magnitude and rate-of-rise that is typically predicted by climate models to accompany the projected future increase in the air's CO2 content. Factoring in plant productivity gains that will occur as a result of the aerial fertilization effect of the ongoing rise in atmospheric CO2, plus its accompanying transpiration-reducing effect that boosts plant water use efficiency, the world's vegetation possesses an ideal mix of abilities to reap a tremendous benefit in the years and decades to come.
Given such findings, the recent "greening of the earth" observed by a host of scientists will likely continue throughout the years and decades to come.