Climate Change, Texas, and the Limits of Confidence John Nielsen-Gammon Dept. of Atmospheric Sciences Texas A&M University
Global Surface Temperature (3)
Pattern of Temperature Trend
Regional Temperatures, 1-2000 (PAGES 2013)
Multiple datasets & analyses (AR5 WG1 FAQ2.1)
Mass change, ice sheets (AR5 WG1 Figs 4.13d-4.14d)
Changes in Water and Ice (AR5 WG1 FAQ2.1)
Global Surface Temperature (3)
Global temperatures
Global temperatures
Global Energy Balance, Part 1 Sun Atmosphere Each arrow = 20 W/m2 Earth
Scientific Principles Energy Imbalance implies a net gain or loss of energy Typical annually averaged energy imbalances are << 1% of the energy flow
Global Energy Balance, Part 1 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 1 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 1 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 1 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 1 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 2 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 2 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 2 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 2 Sun Atmosphere Each arrow = 20 W/m2 Earth
Global Energy Balance, Part 3 Sun Atmosphere To maintain heat flow into atmosphere, Earth must warm too Earth
Detection and Attribution Identify trend: detection Compare with distinct patterns in space and time caused by different forcing agents Apportion role of different forcing agents: attribution
Evolution of Estimated Forcings (AR5 WG1 Fig. 8.18)
Global temperatures
Texas vs Globe
Texas 5-yr Avg vs Globe
Short definition: Weather that’s newsworthy Long definition: two kinds Extreme Weather Short definition: Weather that’s newsworthy Long definition: two kinds Weather that’s extremely unlikely Weather that’s unhealthy or damaging (The same event often fits both definitions)
Melissa Phillip, Houston Chronicle
April 18, 2016
August 28, 2017
August 28, 2017 August 29, 2017
Example #1: Heat and Cold IPCC SREX
The Three Pillars of Sound Attribution
The Three Pillars of Sound Attribution A clear historical trend
The Three Pillars of Sound Attribution Consistent model projections A clear historical trend
The Three Pillars of Sound Attribution Consistent model projections A clear historical trend A sound physical basis
Example #2: Heavy Rain
Climate change’s thermodynamic impact: the size of the pipe The Faucet Climate change’s thermodynamic impact: the size of the pipe + 7% per °C Climate change’s dynamic impact: turning the handle
The size of the pipe matters most when the faucet is wide open
95% confidence interval using effective degrees of freedom estimated following D. A. Griffith & Z. Zhang (1999): Computational Simplifications Needed for Efficient Implementation of Spatial Statistical Techniques in a GIS, Geographic Information Sciences, 5:2, 97-105, DOI: 10.1080/10824009909480519
20% increase ~ 30% trend
Arid Wet
Harris County: 34”
Example #3: Hurricanes
Hurricanes: The Balance of Evidence Increase in peak intensity (1.5 pillars) Decrease in frequency (1 pillar) …but spatially variable (1.5 pillars)
Did Harvey stall because of climate change?
National climate assessment News items Resources IPCC.ch Special report on extremes (SREX) Fifth assessment report, working group 1 (AR5 WG1) National climate assessment News items AP + USA TODAY + NYTIMES ~ Network news
The climate is changing Over the long haul, it’s us Summary The climate is changing Over the long haul, it’s us Future changes are hard to pin down Some impacts are easy It’ll get warmer, it’ll rain harder Some impacts are hard More droughts? Fewer hurricanes?
John W. Nielsen-Gammon n-g@tamu.edu 979-862-2248 Contact Information John W. Nielsen-Gammon n-g@tamu.edu 979-862-2248 http://climatexas.tamu.edu