The Environmental Change Model in Climate Reanalyzer presents projections of regional temperature, precipitation, and other environmental parameters based on global average temperature. The latter, written as “Global ∆T °C”, is actually degrees Celsius above or below the 1850 global average annual temperature.
All the negative values for ∆T (-6 to -0.5°C) correspond with either the Last Glacial Maximum (LGM) or the Little Ice Age. Both of these were cooling periods characterized by larger glaciers and ice sheets and lower sea level. The positive values (1 to 4°C) are associated with future dates. These are the projected date that a given ∆T will occur based on IPCC RCP-8.5. RCP is short for Representative Concentration Pathway, which are climate change projections based on changes in greenhouse gas emissions and atmospheric concentration. In RCP-8.5 atmospheric CO2 concentrations in the year 2100 resulting from increased emissions from human activities are forecasted to be nearly four times that of 1850 concentrations and three times current concentrations.
IPCC is short for Intergovernmental Panel for Climate Change, a UN related science review and advisory group who assemble scenarios like RCP-8.5 from a collection of climate models produced by researchers from around the planet.