A recent paper led by Gerard Wedderburn-Bisshop questions established emissions accounting methods, particularly regarding land use and deforestation, suggesting that agriculture may be a larger contributor to climate change than previously thought.
In September 2023, during a New Times event, Bill Gates made headlines when he dismissed the idea that planting enough trees could solve climate change, stating, "that’s complete nonsense." While Gates is correct in asserting that tree planting alone cannot address climate change, his comments may inadvertently discourage consideration of land use change solutions. This is particularly concerning given new research that reexamines the impact of land use change and deforestation on climate, challenging the established norms of climate science.
The recent study, led by Gerard Wedderburn-Bisshop, Lead Scientist at the World Preservation Foundation, poses a critical question: What human activities have caused present-day warming? While many attribute climate change primarily to fossil fuel combustion, this assertion is based on greenhouse gas accounting conventions established by the Intergovernmental Panel on Climate Change (IPCC) nearly thirty years ago. At that time, the understanding of land-based carbon cycles and the effects of aerosol cooling were limited.
The IPCC's approach has focused heavily on fossil fuel emissions while adopting a practice known as net land carbon accounting. This method allows for the carbon uptake by newly planted trees and crops to offset emissions from deforestation and other land management practices. Consequently, while fossil fuel emissions are fully accounted for, only one-third of carbon released from land use is included in global emissions inventories. The IPCC justifies this by labeling fossil fuel carbon as "truly new carbon" that adds to the biosphere's carbon pool.
However, the authors of the new paper argue that carbon emissions from deforestation of established forestry should also be considered as "truly new carbon." They emphasize that trees and plants do not differentiate between carbon sources, whether from fossil fuels or land use changes.
Another critical aspect of the research is the phenomenon of aerosol cooling. During the COVID-19 lockdowns, many cities experienced clearer skies, highlighting the detrimental health effects of air pollution. According to UNICEF, air pollution causes approximately eight million deaths annually. Efforts to reduce airborne particulates, such as the International Maritime Organisation's 2020 regulations on fuel sulfur content, have significant health benefits. However, these particulates also mask some of the warming effects of greenhouse gases by reflecting sunlight back into space.
The new research aims to incorporate the effects of aerosol cooling into emissions accounting, which has been largely overlooked in existing IPCC conventions.
One of the most significant departures from IPCC conventions in this paper is the proposed use of Effective Radiative Forcing (ERF) instead of Global Warming Potential (GWP) to assess human-caused warming. GWP compares the warming effects of various greenhouse gases relative to carbon dioxide over a specified timeline, typically one hundred years. However, this method has been criticized for its arbitrary nature and for not accurately reflecting the short-term potency of gases like methane.
ERF measures the extent of warming by assessing the balance of incoming and outgoing energy in the atmosphere. Currently, human activities have caused a positive ERF of approximately three watts per square meter, which translates to an immense amount of additional energy heating the planet, comparable to the output of a million nuclear power stations.
The researchers utilized data from various sources, including the Global Carbon Budget and the Potsdam Institute for Climate Research, to analyze the contributions of different sectors to radiative forcing. Their findings reveal:
The paper presents various charts illustrating the relative impact of each sector under different accounting methods. Notably, when applying the proposed ERF methodology and accounting for gross emissions across all sectors, agriculture emerges as the largest contributor to warming, accounting for 60% of effective radiative forcing since 1750, compared to only 18% from fossil fuels.
These findings suggest a need for a paradigm shift in how we approach climate change mitigation. While transitioning away from fossil fuels remains critical, the research highlights the importance of addressing agricultural practices and land use changes. The authors advocate for a comprehensive reevaluation of emissions accounting methods to better reflect the true impact of human activities on climate change.
In conclusion, this new research challenges long-held beliefs about the primary drivers of climate change and underscores the complexity of the issue. It calls for urgent action not only in reducing fossil fuel reliance but also in rethinking our agricultural systems and land management practices. As we move forward, it is essential to consider these findings in the broader context of climate policy and action.
