21st Century Temperature and Precipitation Scenarios from IPCC

Climate models used by the Intergovernmental Panel on Climate Change (IPCC) estimate global temperature and precipitation patterns will change throughout the 21st century because of rising greenhouse gas concentrations. The visualization above is based on one of the four scenarios called Representative Concentration Pathways (RCPs) in which carbon dioxide concentrations reach 670 parts per million (ppm) by 2100, up from around 400 ppm today.

The carbon dioxide concentrations in the year 2100 for each of the four RCPs are:
RCP 2.6: 421 ppm
RCP 4.5: 538 ppm
RCP 6: 670 ppm (shown above)
RCP 8.5: 936 ppm

These four RCPs represent a wide range of potential worldwide greenhouse gas emissions and sequestration scenarios for the coming century. The pathways are numbered based on the expected Watts per square meter – essentially a measure of how much heat energy is being trapped by the climate system – each scenario would produce. The pathways are partly based on the ultimate concentrations of carbon dioxide and other greenhouse gases. There are a few long-term studies like the CARBONO Project in Costa Rica that has been measuring response of tropical trees to increasing atmospheric carbon diokside levels and provide important information to calibrate RCPs.

One significant consequence of increased atmospheric carbon is ocean acidification which unfortunately gets less attention from major media outlets.

Visualizations for other RCPs are included below (no narration):

RCP 2.6: 421 ppm

CMIP5: 21st Century Temperature and Precipitation Scenarios – RCP 2.6: 421 ppm from Nature Documentaries on Vimeo.

In May 2013 levels passed 400 ppm reaching a concentration not seen on the Earth for millions of years. Concentration was less than 300 parts per million at the end of the 19th century. Note that each animation starts with temperature visualizations and switches to precipitation patterns halfway through.

RCP 4.5: 538 ppm

CMIP5: 21st Century Temperature and Precipitation Scenarios – RCP 4.5: 538 ppm from Nature Documentaries on Vimeo.

According to the projections, the largest temperature increases are seen in the northern hemisphere. Across North America, areas that typically have snow, such as the Rocky Mountains and northern Canada, will see the earliest and largest temperature rise. The warming temperatures will eliminate the reflective and cooling effect of the white snow cover. This reduction in albedo is the reason why the Arctic region shows such dramatic warming, as the polar sea ice melts and the darker ocean water absorbs energy from the sun. In turn, the warmer water accelerates the melting of the sea ice. This melting trend is already well documented:

Decline in the Arctic Sea Ice Cover 1979-2011 from Uzay Sezen on Vimeo.

All around the globe, the land areas show a greater increase in temperature than the surrounding ocean waters. Evaporation of the water helps to keep the ocean surface cool, and the deep depths of the ocean have a large capacity to absorb energy before heating up. Of the coast of South America stretches an unusually warm patch of the Pacific Ocean. A cyclical occurrence, known as El NiÑo, causes more precipitation in that area of the Pacific, and affects the climate throughout the region. We can see that happen in this visualization of changes in precipitation. Models project warmer waters and increased precipitation to stretch across the Pacific Ocean to Indonesia as the century progresses. Intertropical Convergence Zone (ITCZ) shifts to the north affecting global rainfall patterns. The monsoons over the Indian subcontinent will bring increased precipitation over a wider area, and eastern Africa and the savannas of the Sahel, could see precipitation increases up to 100%. At the same time, the Mediterranean will experience the opposite, a decrease over 40%. In general, the mid-latitude and sub-tropical dry regions are projected to see less precipitation, while the mid-latitude wet regions could see more precipitation. The poles and high latitudes are expected to also have increased precipitation. For North America, the models indicate more precipitation in the north, and less in the south.

RCP 8.5: 936 ppm

CMIP5: 21st Century Temperature and Precipitation Scenarios – RCP 8.5: 936 ppm from Nature Documentaries on Vimeo.



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