Climate Change Spring 2016 Kyle Imhoff

Let’s start with the big picture (climate forcings)…

Major Forces – Milankovitch Cycles

Major Forces – The Oceans

Major Forces – Volcanic Activity

Major Forces – The Sun

What Do We Know? 4 The previously mentioned forcing mechanisms are well-known, well- understood, and relatively accurately observed 4 These climate forcing mechanisms do not completely explain the current warming trend seen globally

The Greenhouse Effect..

Greenhouse Effect

Carbon Dioxide Output

Greenhouse Effect Courtesy of IPCC

Greenhouse Effect – Water Vapor

What Does This Mean For Global Temperatures?

Global Temperature Trend Courtesy of NASA Global Institute for Space Studies

Global Temperatures by Hemisphere

Comparison of Trends

The Hockey Stick

A modification of the ‘Stick’

Implications for the Mid-Atlantic

Sea Level Rise Predictions

Inland flooding because of increased moisture

So Why The Controversy?

Attribution and Projections 4 The actual temperatures at the surface globally are increasing – this is not in dispute scientifically 4 Why temperatures are rising is another story – “scientific consensus” is a bit misleading –Science is driven by skepticism and disproving previously held beliefs 4 The ability to quantify how much greenhouse gases (specifically CO 2 ) affect temperatures would require a nearly perfect understanding of how all other forcings affect temperatures –Very difficult to do with a high degree of confidence though datasets are getting better

Attribution and Projections 4 There is a statistical argument as well –We have ~150 years of GOOD meteorological observations at the surface –We can reconstruct temperatures back 1000s of years, but these are not as precise (tree rings, ice core data, etc.) –To give perspective to current warming trend is very difficult (too small of a sample size of good data) Is this warming unprecedented Has this kind of warming occurred in the past without other forcings present?

Attribution and Projections 4 Projection Accuracy –How accurate are climate models? –Weather models are known to have flaws/imperfections – climate models are not immune –Climate models are built to match historical information Historical information is imperfect and the future climate system may not react the way scientists think it “should” Think back to the atmosphere being a “chaotic” system by nature

Summary – The Three A’s.. 4 Accuracy – are the observations credible? –Yes, but only for sure in the most recent past –We can at least attempt to estimate errors in reconstruction datasets 4 Attribution – which part is natural variation and which part is due to anthroprogenic sources? –Some is most certainly caused by anthropogenic sources – but by how much –How much does natural variation play a role (do we understand this fully? 4 Adaptation – whatever the cause, we will need to adapt or mitigate… –Knowing that the Earth is warming is enough knowledge to require action in susceptible parts of the globe (coasts, drought-susceptible regions, etc.)