But — not all parts of it are heating up at the same rate. Temperature in the Arctic in particular is rising faster than the global average. The Arctic, according to NASA data, warmed by about 2.2 °C (4 °F) between 1900 and 2015.

Their estimate of Arctic heating is considerably bigger than NASA's. It indicates that between 1900 and 2015, Arctic temperature has risen about 2.9 °C (5.3 °F).

Change in average surface temperature (1986-2005 and 2081-2100)

The oceans have a huge thermal mass compared to the atmosphere and land surface. They act as the planet’s heat storage and transportation system, as the ocean currents redistribute the heat. This is important because if we look at the global surface temperature as an indication of warming, we’re only getting some of the picture. The oceans act as a huge storage heater, and will continue to warm up the lower atmosphere (no matter what changes we make to the atmosphere in the future).

“Charney 1979 Climate Senstivity” is about 3oC for a doubling of CO2. The range shown is for climate sensitivities of 1.5 to 4.5.

Newer studies use different types of scenarios, called Representative Concentration Pathways (RCPs), to predict future climate change. Climate models using the highest of these new concentration pathways, called RCP8.5, suggests four degrees warming as a best estimate for a world scenario where little or no mitigation action is taken.

This shows estimates of global average surface air temperature over the ~540 My of the Phanerozoic, since the first major proliferation of complex life forms on our planet. A substantial achievement of the last 30 years of climate science has been the production of a large set of actual measurements of temperature history (from physical proxies), replacing much of the earlier geological induction (i.e. informed guesses). The graph shows selected proxy temperature estimates, which are detailed below. Because many proxy temperature reconstructions indicate local, not global, temperature -- or ocean, not air, temperature -- substantial approximation may be involved in deriving these global temperature estimates. As a result, the relativities of some of the plotted estimates are approximate, particularly the early ones.

Global average temperature is one of the most-cited indicators of global climate change, and shows an increase of approximately 1.4°F since the early 20th Century. The global surface temperature is based on air temperature data over land and sea-surface temperatures observed from ships, buoys and satellites. There is a clear long-term global warming trend, while each individual year does not always show a temperature increase relative to the previous year, and some years show greater changes than others. These year-to-year fluctuations in temperature are due to natural processes, such as the effects of El Ninos, La Ninas, and the eruption of large volcanoes. Notably, the 20 warmest years have all occurred since 1981, and the 10 warmest have all occurred in the past 12 years.

The globe as a whole warmed by about 1.1 °C (2 °F) between 1900 and 2015.

There aren’t that many full-blown El Niño events, but global temperatures during El Niños seem to be following a steady upward trend. There are more La Niña events, and those global temperatures also clearly follow a steady upward trend. Finally, the temperatures during the many neutral years also show no sign of departing from a steady upward trend. There’s enough scatter in the neutral years that if one had considered the period 1977-1987, or the period 1987-1997, one might be tempted to say that the neutral years had little or no warming. But the past decade fits nicely with the long-term upward trend of 0.16 C/decade shown by all three time series.

Some questions about the role of ENSO in setting records in annual s. We know the El Niño warms the global mean, La Niña cools it, but what happens when statistically correct for that?

Yes. Earth’s average surface air temperature has increased by about 0.8 °C (1.4 °F) since 1900, with much of this increase taking place since the mid-1970s (figure 1a). A wide range of other observations (such as reduced Arctic sea ice extent and increased ocean heat content) and indications from the natural world (such as poleward shifts of temperature-sensitive species of fish, mammals, insects, etc.) together provide incontrovertible evidence of planetary-scale warming.

Figure 2.20. Change in surface air temperature at the end of this century (2081-2100) relative to the turn of the last century (1986-2005) on the coldest and hottest days under a scenario that assumes a rapid reduction in heat trapping gases (RCP 2.6) and a scenario that assumes continued increases in these gases (RCP 8.5). This figure shows estimated changes in the average temperature of the hottest and coldest days in each 20-year period. In other words, the hottest days will get even hotter, and the coldest days will be less cold. (Figure source: NOAA NCDC / CICS-NC).

The average surface temperature of the world's oceans has been increasing since about 1910.

Figure 2.3. Observed global average changes (black line), model simulations using only changes in natural factors (solar and volcanic) in green, and model simulations with the addition of human-induced emissions (blue). Climate changes since 1950 cannot be explained by natural factors or variability, and can only be explained by human factors. (Figure source: adapted from Huber and Knutti29).

The climate curve looks like a “hump”. At the beginning of the Holocene – after the end of the last Ice Age – global temperature increased, and subsequently it decreased again by 0.7 ° C over the past 5000 years. The well-known transition from the relatively warm Medieval into the “little ice age” turns out to be part of a much longer-term cooling, which ended abruptly with the rapid warming of the 20th Century. Within a hundred years, the cooling of the previous 5000 years was undone. - Click here for more information

1.       “ Anders Levermann et al, June 2013 PNAS