Abstract. Anthropogenic increases in atmospheric greenhouse gas concentrations are the main driver of current and future climate change. The integrated assessment community has quantified anthropogenic emissions for the shared socio-economic pathway (SSP) scenarios, each of which represents a different future socio-economic projection and political environment. Here, we provide the greenhouse gas concentrations for these SSP scenarios – using the reduced-complexity climate–carbon-cycle model MAGICC7.0. We extend historical, observationally based concentration data with SSP concentration projections from 2015 to 2500 for 43 greenhouse gases with monthly and latitudinal resolution. CO2 concentrations by 2100 range from 393 to 1135 ppm for the lowest (SSP1-1.9) and highest (SSP5-8.5) emission scenarios, respectively. We also provide the concentration extensions beyond 2100 based on assumptions regarding the trajectories of fossil fuels and land use change emissions, net negative emissions, and the fraction of non-CO2 emissions. By 2150, CO2 concentrations in the lowest emission scenario are approximately 350 ppm and approximately plateau at that level until 2500, whereas the highest fossil-fuel-driven scenario projects CO2 concentrations of 1737 ppm and reaches concentrations beyond 2000 ppm by 2250. We estimate that the share of CO2 in the total radiative forcing contribution of all considered 43 long-lived greenhouse gases increases from 66 % for the present day to roughly 68 % to 85 % by the time of maximum forcing in the 21st century. For this estimation, we updated simple radiative forcing parameterizations that reflect the Oslo Line-By-Line model results. In comparison to the representative concentration pathways (RCPs), the five main SSPs (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) are more evenly spaced and extend to lower 2100 radiative forcing and temperatures. Performing two pairs of six-member historical ensembles with CESM1.2.2, we estimate the effect on surface air temperatures of applying latitudinally and seasonally resolved GHG concentrations. We find that the ensemble differences in the March–April–May (MAM) season provide a regional warming in higher northern latitudes of up to 0.4 K over the historical period, latitudinally averaged of about 0.1 K, which we estimate to be comparable to the upper bound (∼5 % level) of natural variability. In comparison to the comparatively straight line of the last 2000 years, the greenhouse gas concentrations since the onset of the industrial period and this studies' projections over the next 100 to 500 years unequivocally depict a “hockey-stick” upwards shape. The SSP concentration time series derived in this study provide a harmonized set of input assumptions for long-term climate science analysis; they also provide an indication of the wide set of futures that societal developments and policy implementations can lead to – ranging from multiple degrees of future warming on the one side to approximately 1.5 ∘C warming on the other.

El Niño events differ substantially in their spatial pattern and intensity. Canonical Eastern Pacific El Niño events have sea surface temperature anomalies that are strongest in the far eastern equatorial Pacific, whereas peak ocean warming occurs further west during Central Pacific El Niño events. The event types differ in their impacts on the location and intensity of temperature and precipitation anomalies globally. Evidence is emerging that Central Pacific El Niño events have become more common, a trend that is projected by some studies to continue with ongoing greenhouse warming. Here, we identify spatial and temporal patterns in observed sea surface temperatures that distinguish the evolution of Eastern and Central Pacific El Niño events in the tropical Pacific. We show that these patterns are recorded by a network of 27 seasonally resolved coral records, which we then use to reconstruct Central and Eastern Pacific El Niño activity for the past four centuries. We find a simultaneous increase in Central Pacific events and a decrease in Eastern Pacific events during the late 20th century that leads to a ratio of Central to Eastern Pacific events that is unusual in a multi-century context. Compared to the past four centuries, the most recent 30-year period includes fewer, but more intense Eastern Pacific El Niño events. Canonical eastern Pacific (EP) El Niño events exhibit their largest sea surface temperature anomalies (SSTA) in the far eastern tropical Pacific near the Peruvian coast 1. Over recent decades, peak warming during several El Niño events has been displaced approximately 11,000 km, or 100°longitude, westwards into the central equatorial Pacific. These El Niño events are described as Central Pacific (CP) El Niño, warm-pool El Niño 2 , El Niño Modoki 3 , or Dateline El Niño 4. The displacement of maximum SSTA towards the central Pacific drives substantial shifts in atmospheric convection and circulation responses 5-7 , which alter the location and intensity of temperature and precipitation impacts associated with El Niño around the globe 3;4;8-11. Evidence is emerging that changes in El Niño Southern Oscillation (ENSO) behaviour have occurred during the instrumental period 12-15. Following the climate regime shift in 1976/1977, zonal SSTA propagation during El Niño changed from westward to eastward 16. Coincident with the shift to a positive phase of the Interdecadal Pacific Oscillation (IPO) 16-18 in 1999/2000, Pacific trade winds have strengthened 19;20. Observations indicate increasing El Niño event amplitude 21 , strong decadal variations in event frequency 22 , changes in maximum SSTA propagation direction 12;23 and delays in the onset of El Niño events 24. Since the late 1990s there has been a higher number of CP events relative to EP events, unprecedented in instrumental records 2;21;22. It is unclear whether this recent increase is part of natural climate variability 25 or a consequence of anthropogenic climate change 22. A precise picture of El Niño diversity is a challenge due to model def...