Because projections of climate change depend heavily upon future human activity, climate models are run against scenarios. There are 40 different scenarios, each making different assumptions for future greenhouse gas pollution, land-use and other driving forces.BEST SCENARIO: B1WORST SCENARIO: A1FI
BEST SCENARIO: B1WORST SCENARIO: A2
BEST SCENARIO: A1TWORST SCENARIO: A1FI
Albedo means reflectivity
Darker = higher change °C
Temperature projections to the year 2100, based on a range of emission scenarios and global climate models. Scenarios that assume the highest growth in greenhouse gas emissions provide the estimates in the top end of the temperature range. The orange line (“constant CO2”) projects global temperatures with greenhouse gas concentrations stabilized at year 2000 levels.
Orange = less precipitationGreen = more precipitationWhite = no change
Past and projected global average sea level. The gray shaded area shows the estimates of sea level change from 1800 to 1870 when measurements are not available. The red line is a reconstruction of sea level change measured by tide gauges with the surrounding shaded area depicting the uncertainty. The green line shows sea level change as measured by satellite. The purple shaded area represents the range of model projections for a medium growth emissions scenario.
A) Atmospheric CO2 concentrations,B) global ocean pH, C) and the surface saturation of aragonite (crystal formof calcium carbonate). The dashed line represents the 100%line separating over- and under-saturated regions. The Southern Ocean could be aragonite under-saturated by about 2050, making it difficult or impossible for certain corals and other marine calcifiers to form shells.
Green indicates countries that have signed and ratified the treaty, grey is not yet decided, and red is no intention of ratifying.GREY = AFGHANISTAN, SOMALIA, WESTERN SAHARA, TAIWANRED = US
The Case for Human-Made Climate Change<br />Part II<br />
State of Knowledge<br />Certain<br />Atmospheric levels of greenhouse gases have risen<br />Result of burning fossil fuel<br />Earth warmed 1.3°F <br />Very Likely<br />Rising atmospheric levels of greenhouse gases contribute to climate change<br />Uncertain<br />How much warming will occur<br />How fast warming will occur<br />How warming affects the climate<br />