RCP26
This scenario requires that carbon dioxide levels will decline to zero by 2100, starting in 2020. It is likely to keep global temperature rise below 2 degrees Celsius by 2100.
RCP45
This scenario requires that by 2100, carbon dioxide levels will be half of that in 2050, starting to decline in 2045. It is likely keep global temperature rise 2-3 degrees Celsius by 2100. Many organisms will be unable to survive in environments from this and future scenarios (like RCP60 and RCP85 in this model).
RCP60
This scenario requires that carbon dioxide levels start declining in 2080, and is likely to keep global temperature rise 3-4 degrees Celsius by 2100.
RCP85
This scenario requires that carbon dioxide levels continue to rise through 2100. It is deemed the "worst-case" scenario.
Image Credit: By Efbrazil - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=87801257