Climate Change: Natural Temperature Variations and Causes, Papers of Meteorology

Download Climate Change: Natural Temperature Variations and Causes and more Papers Meteorology in PDF only on Docsity! Chapter 19: Climate Change From a perspective of millions of years, we are now in a cold era (ice age). During the warmer periods, there was no ice in the poles! Sea level would be 213 ft higher than now. The warmer eras were ~ 10°C warmer than now. (See Fig. 19.11) Natural temperature variations are large over large timescales (5°C in 10,000 yrs) and have a drastic affect on climate. Measuring temperature variations: 1. Oxygen isotope method – Stable isotopes of oxygen Abundance O 168 99.76% O 178 0.038% O 188 0.20% Because O18 is heavier, it doesn’t evaporate as readily. 2. Dendrochronology – Look at tree rings to see temperature and precipitation history. Compare rings hundreds of years ago in long–lived trees with rings of recent trees when climate known. 3. Ocean sediment cores- Existence of fossils of certain organisms can give temperature range. Ocean Concentrated O18 Glacier Concentrated O16 During cold eras, ocean is low and has increased O18 Causes of Climate Change • Plate tectonics Movement of oceanic plates cause volcanic eruptions (CO2, H2O, SO2) which can influence climate. See fig 19.14 for eruption of Mt. Pinatubo. Influence is over millions of years. • Variations in Earth’s orbit Eccentricity – period ~ 100,000 yrs Precession – period ~ 23,000 yrs Obliquity – period ~ 41,000 yrs (22° - 24.5°) Milankovitch theory – supported by climate data • Variations in CO2 (fig 19.11) from analysis of trapped air bubbles. Note: CO2 concentration now is 360 ppm! It was ~290 ppm 100 yrs ago • Atmospheric particles Sulfates from pollution and phytoplankton - effect is to cool atmosphere Volcanic eruptions (high in sulfur)(fig 19.14) – Little Ice Age correlates to acidic ice uncovered from AD 1350 → 1700. • Variations in solar output Sunspots – max every ~ 11 yrs Magnetic cycle – 22 yr cycle (Magnetic field reverses every ~11 yrs) (See fig from paper – shown in class) Almost no sunspots 1645 – 1715 Maunder minimum – corresponds to Little Ice Age. CO2 and Global Warming Now: CO2 is ~ 360ppm This is expected to double within 100 yrs. Most climate models predict doubling of CO2 will lead to warming of surface air of 1.5° to 4.5°C (2.7 to 8.1°F).