page_title: Attribution of recent climate change
section_title: "Fingerprint" studies
hierarchical_section_title: Attribution of recent climate change / Attribution of 20th-century climate change / Details on attribution / "Fingerprint" studies
caption_attribution_description: English: Graph showing global warming attribution - based on NCA4 (2017) Fig 3.3. Modeled forcing responses of forces affecting global temperature (1870 - ~2017). Uploader took separate charts, changed them in Photoshop to a common vertical (temperature anomaly) scale, and merged them into this composite graphic. Source of charts from which the above composite chart was formed: Climate Science Special Report: Fourth National Climate Assessment, Volume I - Chapter 3: Detection and Attribution of Climate Change.&#32;science2017.globalchange.gov.&#32;U.S. Global Change Research Program (USGCRP)&#32;(2017). Archived from the original on September 23, 2019. Adapted directly from Fig. 3.3. Archive of the PNG image itself. Globalchange.gov Fig. 3.3 credits this Atmospheric Chemistry and Physics article which states: "Atmos. Chem. Phys., 13, 3997-4031, 2013, https://doi.org/10.5194/acp-13-3997-2013, © Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License."
context_page_description: Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent global warming and related climate changes on Earth. The effort has focused on changes observed during the period of instrumental temperature record, particularly in the last 50 years. This is the period when human activity has grown fastest and observations of the atmosphere above the surface have become available. According to the Intergovernmental Panel on Climate Change, it is "extremely likely" that human influence was the dominant cause of global warming between 1951 and 2010. Likely human contribution is 93%–123% of the observed 1951–2010 temperature change.
  Some of the main human activities that contribute to global warming are:
  increasing atmospheric concentrations of greenhouse gases, for a warming effect
  global changes to land surface, such as deforestation, for a warming effect
  increasing atmospheric concentrations of aerosols, mainly for a cooling effect
  In addition to human activities, some natural mechanisms can also cause climate change, including for example, climate oscillations, changes in solar activity, and volcanic activity.
context_section_description: Finally, there is extensive statistical evidence from so-called "fingerprint" studies. Each factor that affects climate produces a unique pattern of climate response, much as each person has a unique fingerprint. Fingerprint studies exploit these unique signatures, and allow detailed comparisons of modelled and observed climate change patterns. Scientists rely on such studies to attribute observed changes in climate to a particular cause or set of causes. In the real world, the climate changes that have occurred since the start of the Industrial Revolution are due to a complex mixture of human and natural causes. The importance of each individual influence in this mixture changes over time. Of course, there are not multiple Earths, which would allow an experimenter to change one factor at a time on each Earth, thus helping to isolate different fingerprints. Therefore, climate models are used to study how individual factors affect climate. For example, a single factor (like greenhouse gases) or a set of factors can be varied, and the response of the modelled climate system to these individual or combined changes can thus be studied.
  These projections have been confirmed by observations (shown above).}}
  For example, when climate model simulations of the last century include all of the major influences on climate, both human-induced and natural, they can reproduce many important features of observed climate change patterns. When human influences are removed from the model experiments, results suggest that the surface of the Earth would actually have cooled slightly over the last 50 years. The clear message from fingerprint studies is that the observed warming over the last half-century cannot be explained by natural factors, and is instead caused primarily by human factors.
  Another fingerprint of human effects on climate has been identified by looking at a slice through the layers of the atmosphere, and studying the pattern of temperature changes from the surface up through the stratosphere (see the section on solar activity). The earliest fingerprint work focused on changes in surface and atmospheric temperature. Scientists then applied fingerprint methods to a whole range of climate variables, identifying human-caused climate signals in the heat content of the oceans, the height of the tropopause (the boundary between the troposphere and stratosphere, which has shifted upward by hundreds of feet in recent decades), the geographical patterns of precipitation, drought, surface pressure, and the runoff from major river basins.
  Studies published after the appearance of the IPCC Fourth Assessment Report in 2007 have also found human fingerprints in the increased levels of atmospheric moisture (both close to the surface and over the full extent of the atmosphere), in the decline of Arctic sea ice extent, and in the patterns of changes in Arctic and Antarctic surface temperatures.
  The message from this entire body of work is that the climate system is telling a consistent story of increasingly dominant human influence – the changes in temperature, ice extent, moisture, and circulation patterns fit together in a physically consistent way, like pieces in a complex puzzle.
  Increasingly, this type of fingerprint work is shifting its emphasis. As noted, clear and compelling scientific evidence supports the case for a pronounced human influence on global climate. Much of the recent attention is now on climate changes at continental and regional scales, and on variables that can have large impacts on societies. For example, scientists have established causal links between human activities and the changes in snowpack, maximum and minimum (diurnal) temperature, and the seasonal timing of runoff over mountainous regions of the western United States. Human activity is likely to have made a substantial contribution to ocean surface temperature changes in hurricane formation regions. Researchers are also looking beyond the physical climate system, and are beginning to tie changes in the distribution and seasonal behaviour of plant and animal
caption: Top panel: Observed global average temperature change (1870— ).
   Bottom panel: Data more recent than that plotted at left, and merged for display on the same axis to emphasize relative strengths of forces affecting temperature change. Human-caused forces have increasingly dominated.
exif: {}