The Climate Science Behind The Green New Deal - A Layperson's Explanation

- Feb 25, 2019-

One of the darling headlines of the moment is the Green New Deal.It is all over the place and that is a good thing irrespective of what you think of the actual policies within it.It means there is an actual conversation about climate change and its solutions.Such conversations have been hard to come by over the past several years.Much of what I have seen written in Forbes and elsewhere focuses on the costs, politics, and challenges associated with the Green New Deal.Critics opine about its costs and smell of socialism.Supporters argue that the costs of not doing it are far worsefor the planet and our longer term economy.I have seen very little written on the details of the science guiding the deal.Here is a layperson's guide to that part of the plan.

Before I get to the science, a quick refresher in history is required.The New Dealwas a sweeping set of initiatives and policies of President Franklin D. Roosevelt to help lift the stifling grip that the Great Depression had on the U.S. economy and its prosperity.The Great Depression was viewed as a singular and crippling threat to the nation and global markets.Senator Ed Markey (D-MA) and Rep. Alexandria Ocasio-Cortez (D-NY) view carbon and climate change in the same way so introduced a Green New Deal.To be fair, the term has been around for a while, andthere are various "Green New Deal" proposals.Herein, I am focusedon the proposed legislationintroduced by Markey and AOC.

The legislation is anchored in science.The report firmly cites the guidance of science in theIntergovernmental Panel on Climate Changeand theNovember 2018 Fourth National Climate Assessment report.The Green New Deal seamlessly integrates climate change within broader socio-economic grand challenges.For example, it points out that "whereas climate change, pollution, and environmental destruction have exacerbated systemic racial, regional, so-, environmental, and economic injustices" It is this part of the deal that is sending some policymakers and pundits into orbit, but I will not deal with those aspects.Instead, I want to focus onthe key climate science pointsunderpinning the legislation.

Human activity is a key contributor to climate change in the past 100 years.Yes, scientists know climate changes naturally and always has.As a climate scientist, I hear this often from some corners.We know, we know.However, grass always grew naturally before fertilizer was invented.Trees definitely fell in the forest naturally, but a chainsaw can do the trick too.Climate change is not an "either/or" proposition.The naturally-varying system is now being altered by human activity, and virtually every major report and credible scientific organization has stated this fact.

Sea level rise and extreme weather events are threats to our economy, infrastructure, and safety. I recently wrote a piece in Forbes laying out multiple ways that climate change is a threat and even rises to the level of a national emergency.Increasingly, lawmakers fromboth sides of the aisleare recognizing that this is not just about polar bears butconstituent's kitchentable issues.

The 2 degree C (3.6 degrees F for those of us in the U.S.)tipping point is critical.An important premise of the Paris Agreement was to address carbon emissions so that global warming does notexceed the 2 degree threshold.Like any tipping point, any step beyond that point causes irreversible change.As an analogy, stretching elastic too far may cause it to exceed its "snapback" point.TheParis Agreement actually targeted 1.5 degrees C as a safety buffer.As alluded to earlier, climate changes due to Earth'sorbital changes (Milankovitch cycles), volcanic emissions, changes in the sun's output, mountain-building and more.However, the figure below points out that none of these changes affect the climate system more than greenhouse gases emission.I often use the analogy of greenhouse gases being the "apples" in an apple pie recipe.The cinnamon, sugar, and flour are important, but the apples are the dominant ingredient.As I previously wrote in Forbes,

climate sensitivity is the amount of warming as a function of the greenhouse gas forcing and various processes that I just mentioned while accounting for various feedbacks.There is ongoing climate discussion, as any good science community should, on the level of climate sensitivity.A few scholars argue that the 2 degree number is too aggressive, and others suggest it is too conservative

A de-carbonized economy will be required.The proposed legislation is adamant that global greenhouse gas emissions must be 40 to 60 percent from 2010 levels by 2030 and net-zero by 2050.This will be seen as overly aggressive by some and a threat to the current fossil-fuel based economy.To accomplish this goal, a new renewable energy economy would have to drive the agenda along with technological innovation.Professor Mark Jacobson at Stanford Universityhas been a long-time leader in climate science and renewable energy transition.Many of the assumptions in the Green New Deal seem to be anchored in his scholarship.According to,

The Jacobson plan – which, while only one potential approach, is currently the most detailed and well-known – would be met with 30.9% onshore wind, 19.1% offshore wind, 30.7% utility-scale photovoltaics (PV), 7.2% rooftop PV, 7.3% concentrated solar power (CSP) with storage, 1.25% geothermal power, .37% wave power, 0.14% tidal power, and 3.01% hydroelectric power.

Jennie Stephens is a professor of sustainability science and policy at Northeastern University.In aUniversity issued press release, she said, "not only would a transition to renewable energy drastically slow the pace of global warming, it could also be the catalyst for the creation of millions of jobs, the equitable distribution of power, and the creation of healthier communities that are better suited to bounce back from disaster."I suspect others disagree with her, but this has always been the crux of the discussion about climate change, the solution space.There are perceived "winners" and "losers" in a move from the status quo economy akin to Upton Sinclair's great quote, "it is difficult to get a man to understand something when his salary depends upon his not understanding it."

The debate will rage on.If and when legislation is passed, it will look nothing like what has been put forth.The art, science, and horror of lawmaking always involves compromise and at least there is a conversation.


Dr. Marshall Shepherd, Dir., Atmospheric Sciences Program/GA Athletic Assoc.Distinguished Professor (Univ of Georgia), Host, Weather Channel's Popular Podcast, Weather Geeks, 2013 AMS President