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New Climate Reports Lay Down a Challenge


Two new climate science reports were released last fall and highlight the continuing peril of climate change.

The first new report, Global Warming of 1.5 °C, was produced by the Intergovernmental Panel on Climate Change (IPCC). The 195 countries that joined the Paris Climate Agreement in 2015 pledged to take action to limit global warming to 2 degrees Celsius (3.6 °F). The new report shows that limiting total warming to 1.5 °C would be far better for the environment. A second report, the Fourth National Climate Assessment, focuses on climate change impacts on various sectors and regions of the United States. This report warns of reduced agricultural productivity and changes in forest structure and function. The report describes many actions individuals and groups can take to reduce the impact of climate change.

The IPCC’s special report on Global Warming of 1.5 °C grew out of the Paris Climate Agreement.

The global agreement not only aimed to limit global temperature rise to well below 2 °C, but also sought to identify the implications of a 1.5 °C goal. According to the IPCC, keeping global temperatures below 1.5 °C would require that net greenhouse gas emissions be halved from 2010 levels by 2030 and reach net zero by 2050. This finding was carried by major newspapers like the New York Times, the Washington Post, and the Guardian. The planet has already warmed by about 1 °C in the last hundred years.  Added human-caused warming of about 0.2 °C per decade means that 1.5 °C of warming is only decades away, likely arriving sometime between 2030 and 2052. Despite these dire headlines, the IPCC report also tried to inspire a sense of hope and action. For instance, the report noted that the effects of global warming on coral reefs, Arctic sea ice, and sea level rise would be less severe if global temperatures could be held below 1.5 °C. And here in the Northeast, staying under 1.5 °C means heat waves and intense rains would be less extreme and occur less often than with 2 °C or more of warming.     

The Fourth National Climate Assessment describes more specific impacts for the United States as a whole, and the Northeast specifically.

The main climate trends for the Northeast are increases in rainfall intensity, changes in the timing of rainfall, increases in temperature, and decreased seasonality. The increase in the intensity of rainfall can cause more soil compaction, delays in planting, and reduce the number of days when fields are workable. Heavy rains also lead to added soil erosion and can cause the runoff of manure, fertilizers and pesticides. The timing of rainfall will change with more during the winter and spring but little change in the summer. Higher summer temperatures and no extra summer rain may lead to more short- or mid-term droughts. This may be made worse by the trend of more rain falling in large events separated by longer periods of dryness. The result could oddly be dryer soils under a wetter climate, which could have a negative impact on crop and forest productivity, and result in increased costs for irrigation. Warmer temperatures overall will have a positive impact on agriculture and forestry by extending the growing season. However, warmer springs and earlier budbreak and flowering may make certain species more subject to late spring frosts. Increases in extreme heat may challenge livestock health and increase costs for ventilation and shade. Taken together, observed and projected changes in climate in the Northeast may have some benefits to agriculture and forestry, but may also pose additional risks and costs.

The key question going forward is how we choose to respond to the challenges outlined by the IPCC and the Fourth National Climate Assessment. As both reports make clear, our climate is changing rapidly. On February 6, NASA and NOAA reported that 2018 was the 4th warmest year of the modern era. This means that the 5 warmest years ever recorded have been the last 5 years. The clear environmental impacts happening globally and here in the Northeast have occurred with only 1 °C of warming. In the near term, managing unavoidable impacts to key sectors, like forestry and agriculture, is a challenge that can be met by climate adaptation measures. Adapting to climate change is the central mission of USDA’s Northeast Climate Hub. Over the long term, an even greater challenge will be how to avoid some of the potentially unmanageable outcomes that are more likely at higher levels of warming, especially beyond 2 °C. This will certainly require a greater emphasis on mitigation practices that help farmers and foresters in the Northeast reduce their greenhouse gas emissions. We ask you all to help share your solutions for adapting to these changes and reducing emissions.

By David Hollinger, Director, USDA Northeast Climate Hub