Geoscience Reference
In-Depth Information
Summary
Over the last 150 years, significant changes in climate have been recorded, which are
markedly different from the last at least 2,000 years. These changes include a 0.85°C in-
crease in average global temperatures, sea-level rise of over 20 cm, significant shifts in the
seasonality and intensities of precipitation, changing weather patterns, and the significant
retreat of Arctic sea ice and nearly all continental glaciers. According to the US National
Oceanic and Atmospheric Administration between 1880 and the beginning of 2014, the 13
warmest years on record have all occurred within the last 16 years, with 2010 the warmest
year, followed by 2005, 1998, 2003, 2013, 2002, 2006, 2007, 2009, 2004, 2012, 2001, and
2011. The IPCC 2013 report states that the evidence for climate change is unequivocal and
there is very high confidence that this warming is due to human emissions of GHGs. This
statement is supported by six main lines of evidence: (1) the rise in GHGs in the atmo-
sphere has been measured and the isotopic composition of the gases shows that the major-
ity of the additional carbon comes from the burning of fossil fuels; (2) laboratory and atmo-
spheric measurements show that these gases absorb heat; (3) significant changes in global
temperatures and sea-level rise have been observed over the last century; (4) other signific-
ant changes have been observed in cryosphere and atmosphere including retreating sea ice
and glaciers, and extreme weather events; (5) there is clear evidence that natural processes
including sun spots and volcanic eruptions can not explain the warming trend over the last
100 years; and (6) we now understand the longer term past climate changes and the role
GHGs have played in regulating the climate of our planet.
