<p>From the <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_TS_FINAL.pdf#page=28" rel="noreferrer">IPCC Fifth Assessment Report</a> (2014 / current):</p>

<blockquote>
  <p>It is extremely likely that human activities caused more than half of the observed increase in global average surface temperature from 1951 to 2010. This assessment is supported by robust evidence from multiple studies  using  different  methods.  In  particular,  the  temperature  trend  attributable to all anthropogenic forcings combined can be more closely constrained in multi-signal detection and attribution analyses. Uncertainties in forcings and in climate models’ responses to those forcings, together  with  difficulty  in  distinguishing  the  patterns  of  temperature  response due to WMGHGs and other anthropogenic forcings, prevent as precise a quantification of the temperature changes  attributable to WMGHGs  and  other  anthropogenic  forcings  individually.  Consistent  with AR4, it is assessed that more than half of the observed increase in global average surface temperature from 1951 to 2010 is very likely due  to  the  observed  anthropogenic  increase  in  WMGHG  concentrations.  WMGHGs  contributed  a  global  mean  surface  warming  likely to  be  between  0.5°C  and  1.3°C  over  the  period  between  1951  and  2010, with the contributions from other anthropogenic forcings likely to be between –0.6°C and 0.1°C and from natural forcings likely to be between –0.1°C and 0.1°C. Together these assessed contributions are consistent  with  the  observed  warming  of  approximately  0.6°C  over  this period (Figure TS.10). {10.3}</p>
</blockquote>

<p><a href="https://i.sstatic.net/X3sMX.jpg" rel="noreferrer"><img src="https://i.sstatic.net/X3sMX.jpg" alt="&quot;Likely&quot; ranges and midpoints for warming trends 1951-2010"></a></p>

<p>Observed: temperature measurements</p>

<p>WMGHG or GHG: Well-mixed greenhouse gases like CO2</p>

<p>ANT: Sum of GHG and OA</p>

<p>OA: Other anthropogenic forcings on temperature like aerosols and black carbon</p>

<p>NAT: Natural variability such as change in solar radiation
Internal Variability: Estimated lack of knowledge in current earth models</p>

CC BY-SA 4.0
2019-02-21T09:09:04.300Z
Nice simple answer perfectly on point to the question asked from a rather central source!  Glad you put in the time to add the answer!
JeopardyTempest
CC BY-SA 4.0
2019-02-18T16:56:59.027Z
2019-02-26T18:22:48.910Z
2019-02-26T18:22:48.910Z
elliot svensson
<p>Firstly it is worth demonstrating that 97% of climate scientists agree that climate-warming trends over the past century are very likely due to human activities.</p>

<blockquote>
  <p>W. R. L. Anderegg, “Expert Credibility in Climate Change,” Proceedings
  of the National Academy of Sciences Vol. 107 No. 27, 12107-12109 (21
  June 2010); DOI: 10.1073/pnas.1003187107.</p>
  
  <p>P. T. Doran &amp; M. K. Zimmerman, "Examining the Scientific Consensus on
  Climate Change," Eos Transactions American Geophysical Union Vol. 90
  Issue 3 (2009), 22; DOI: 10.1029/2009EO030002.</p>
  
  <p>N. Oreskes, “Beyond the Ivory Tower: The Scientific Consensus on
  Climate Change,” Science Vol. 306 no. 5702, p. 1686 (3 December 2004);
  DOI: 10.1126/science.1103618.</p>
</blockquote>

<p>But what percentage of the increase is attributed to humans?  Probably almost of all of it.</p>

<p>The scientist Gavin Schmidt from NASA was asked this question on <a href="http://www.realclimate.org/?comments_popup=1853#comment-142358" rel="noreferrer">realclimate.org</a></p>

<p>His response was as follows:</p>

<blockquote>
  <p>Over the last 40 or so years, natural drivers would have caused
  cooling, and so the warming there has been (and some) is caused by a
  combination of human drivers and some degree of internal variability.
  I would judge the maximum amplitude of the internal variability to be
  roughly 0.1 deg C over that time period, and so given the warming of
  ~0.5 deg C, I'd say <strong>somewhere between 80 to 120% of the warming.</strong>
  Slightly larger range if you want a large range for the internal
  stuff. <em>[emphasis added]</em></p>
</blockquote>

<p>The rapid increase in the human-driven component of the forcing are increasingly dwarfing the small, slow natural forcings, rendering them increasingly irrelevant.</p>

<p><img src="https://i.sstatic.net/epPSa.jpg" alt="enter image description here"></p>

CC BY-SA 3.0
2014-04-30T20:10:59.923Z
I think it would make sense to stick at least a nod to the IPCC in this answer, fwiw, instead of leaving it languishing in comments on the original question.
kaberett
CC BY-SA 3.0
2014-04-16T07:43:02.440Z
You may wonder how humans can be responsible for more than 100% of the warmings.  I imagine Gavin is referring to the fact that in the absence of a natural cooling trend, the temperature increase due to humans would be even greater.
Kenshin
CC BY-SA 3.0
2014-04-16T08:00:44.527Z
I think the 120% is better explained as *all* the warming, plus the negation of cooling that would otherwise have happened. (That is, negative cooling = warming).
naught101
CC BY-SA 3.0
2015-10-03T12:38:10.107Z
Good quality surveys of scientific opinion agree there is a consensus on warming but that it is closer to 80% not 97%. And scientific truth is not decided by consensus. Having said that basic science suggests CO2 is a greenhouse gas. What is harder to calculate is how much other atmospheric components exaggerate the basic effect. Also uncertain is how normal atmospheric cycles contribute since reliable temperature records are short. So there is still *some* uncertainty in the human contribution.
matt_black
CC BY-SA 3.0
2014-04-16T07:42:07.570Z
2014-05-01T02:52:14.460Z
2014-05-01T02:52:14.460Z
Kenshin
<p>Approximately what proportion of the global warming seen over the the last century is attributed to anthropogenic sources?</p>

CC BY-SA 3.0
2014-04-20T18:22:50.357Z
I have narrowed the question to focus on "scientific consensus" and have voted to re-open it in its current form.
Tom Au
CC BY-SA 3.0
2014-04-21T00:33:27.060Z
Sorry @TomAu, but I really don't like that edit - it changes the question significantly, to something I did not intend.
naught101
CC BY-SA 3.0
2014-04-21T00:35:17.307Z
There is only one answer to this question, albeit a probabilistic one. The list of "other sources" included will be very small, assuming only significant sources are mentioned. I don't see how this question is too broad - can someone explain?
naught101
CC BY-SA 3.0
2014-04-21T00:39:25.657Z
Up to you. I put the question in a form that is "standard" for other SE sites (I have over 2K rep on several). "Scientific consensus" was sort of a code for "significant sources." Maybe you could reword your question with "significant sources," or "significant scientific sources." But you should make clear that you're asking for "expert" opinion, not ours, except to the extent that we cite experts.
Tom Au
CC BY-SA 3.0
2014-04-21T00:58:56.367Z
Hrm... it's a science site. I would think it would be obvious that I'm looking for answers that rely on up-to-date, peer-reviewed and broadly accepted scientific sources. However, your comment does make me think that the "other sources" part of the question is perhaps making the question too broad (and may even be redundant), so I will remove that.
naught101
CC BY-SA 3.0
2014-04-21T14:17:40.477Z
The changes you made were "good enough" so that I didn't need to retract my "reopen" vote.
Tom Au
CC BY-SA 3.0
2014-04-16T01:12:45.250Z
This is a very debatable topic - research has been done and many different answers have been concluded. When answering, please back up your information!
hichris123
CC BY-SA 3.0
2014-04-16T01:25:54.490Z
Absolutely - reliable citations are a must before I will consider accepting an answer :) Obviously there is significant uncertainty in such attribution, so it would be good to address that in the answer too.
naught101
CC BY-SA 3.0
2014-04-16T01:28:15.687Z
Safe to say that it is greater than zero percent. Not sure if we have a concrete answer beyond that.  "Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities" http://climate.nasa.gov/scientific-consensus
DrewP84
CC BY-SA 3.0
2014-04-16T01:34:32.807Z
There have been detection and attribution studies done before (and I believe these are discussed in the IPCC reports). I think it would be better to rely on these than than on opinion polls (not saying that those polls aren't valid).
naught101
CC BY-SA 3.0
2014-04-16T02:54:39.183Z
Big question! I feel like I'd just be summarising [IPCC AR5 WGI](http://ipcc.ch/report/ar5/wg1/)'s Chapter 10 on attribution if I had a go at it, since I'm not an attribution expert.
jimjamslam
CC BY-SA 3.0
2014-04-16T03:23:46.960Z
@rensa Considering that that sums up the state of the knowledge, that would be as good an answer as likely possible.
gerrit
<climate><human-influence><climate-change><global-warming>
How much of the current global warming is due to human influence?
naught101
# How much of the current global warming is due to human influence?

(Asked by: username_0 on 2014-04-16)

Approximately what proportion of the global warming seen over the the last century is attributed to anthropogenic sources?

**Tags:** climate, human-influence, climate-change, global-warming

> **Comments:**
> **username_2**: This is a very debatable topic - research has been done and many different answers have been concluded. When answering, please back up your information!  
> **username_0**: Absolutely - reliable citations are a must before I will consider accepting an answer :) Obviously there is significant uncertainty in such attribution, so it would be good to address that in the answer too.  
> **username_3**: Safe to say that it is greater than zero percent. Not sure if we have a concrete answer beyond that.  "Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities" http://climate.nasa.gov/scientific-consensus  
> **username_0**: There have been detection and attribution studies done before (and I believe these are discussed in the IPCC reports). I think it would be better to rely on these than than on opinion polls (not saying that those polls aren't valid).  
> **username_4**: Big question! I feel like I'd just be summarising [IPCC AR5 WGI](http://ipcc.ch/report/ar5/wg1/)'s Chapter 10 on attribution if I had a go at it, since I'm not an attribution expert.  
> **username_5**: @rensa Considering that that sums up the state of the knowledge, that would be as good an answer as likely possible.  
> **username_1**: I have narrowed the question to focus on "scientific consensus" and have voted to re-open it in its current form.  
> **username_0**: Sorry @username_1, but I really don't like that edit - it changes the question significantly, to something I did not intend.  
> **username_0**: There is only one answer to this question, albeit a probabilistic one. The list of "other sources" included will be very small, assuming only significant sources are mentioned. I don't see how this question is too broad - can someone explain?  
> **username_1**: Up to you. I put the question in a form that is "standard" for other SE sites (I have over 2K rep on several). "Scientific consensus" was sort of a code for "significant sources." Maybe you could reword your question with "significant sources," or "significant scientific sources." But you should make clear that you're asking for "expert" opinion, not ours, except to the extent that we cite experts.  
> **username_0**: Hrm... it's a science site. I would think it would be obvious that I'm looking for answers that rely on up-to-date, peer-reviewed and broadly accepted scientific sources. However, your comment does make me think that the "other sources" part of the question is perhaps making the question too broad (and may even be redundant), so I will remove that.  
> **username_1**: The changes you made were "good enough" so that I didn't need to retract my "reopen" vote.  

---

## 2 answers

### Answer by username_8 on 2014-04-16. Score: 28 | Accepted answer

Firstly it is worth demonstrating that 97% of climate scientists agree that climate-warming trends over the past century are very likely due to human activities.

> W. R. L. Anderegg, “Expert Credibility in Climate Change,” Proceedings
> of the National Academy of Sciences Vol. 107 No. 27, 12107-12109 (21
> June 2010); DOI: 10.1073/pnas.1003187107.
>
> P. T. Doran & M. K. Zimmerman, "Examining the Scientific Consensus on
> Climate Change," Eos Transactions American Geophysical Union Vol. 90
> Issue 3 (2009), 22; DOI: 10.1029/2009EO030002.
>
> N. Oreskes, “Beyond the Ivory Tower: The Scientific Consensus on
> Climate Change,” Science Vol. 306 no. 5702, p. 1686 (3 December 2004);
> DOI: 10.1126/science.1103618.

But what percentage of the increase is attributed to humans? Probably almost of all of it.

The scientist Gavin Schmidt from NASA was asked this question on [realclimate.org](http://www.realclimate.org/?comments_popup=1853#comment-142358)

His response was as follows:

> Over the last 40 or so years, natural drivers would have caused
> cooling, and so the warming there has been (and some) is caused by a
> combination of human drivers and some degree of internal variability.
> I would judge the maximum amplitude of the internal variability to be
> roughly 0.1 deg C over that time period, and so given the warming of
> ~0.5 deg C, I'd say **somewhere between 80 to 120% of the warming.**
> Slightly larger range if you want a large range for the internal
> stuff. *[emphasis added]*

The rapid increase in the human-driven component of the forcing are increasingly dwarfing the small, slow natural forcings, rendering them increasingly irrelevant.

![enter image description here](https://i.sstatic.net/epPSa.jpg)

> **Comments:**
> **username_8**: You may wonder how humans can be responsible for more than 100% of the warmings.  I imagine Gavin is referring to the fact that in the absence of a natural cooling trend, the temperature increase due to humans would be even greater.  
> **username_0**: I think the 120% is better explained as *all* the warming, plus the negation of cooling that would otherwise have happened. (That is, negative cooling = warming).  
> **username_9**: I think it would make sense to stick at least a nod to the IPCC in this answer, fwiw, instead of leaving it languishing in comments on the original question.  
> **username_10**: Good quality surveys of scientific opinion agree there is a consensus on warming but that it is closer to 80% not 97%. And scientific truth is not decided by consensus. Having said that basic science suggests CO2 is a greenhouse gas. What is harder to calculate is how much other atmospheric components exaggerate the basic effect. Also uncertain is how normal atmospheric cycles contribute since reliable temperature records are short. So there is still *some* uncertainty in the human contribution.  

---

### Answer by username_6 on 2019-02-18. Score: 10

From the [IPCC Fifth Assessment Report](https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_TS_FINAL.pdf#page=28) (2014 / current):

> It is extremely likely that human activities caused more than half of the observed increase in global average surface temperature from 1951 to 2010. This assessment is supported by robust evidence from multiple studies using different methods. In particular, the temperature trend attributable to all anthropogenic forcings combined can be more closely constrained in multi-signal detection and attribution analyses. Uncertainties in forcings and in climate models’ responses to those forcings, together with difficulty in distinguishing the patterns of temperature response due to WMGHGs and other anthropogenic forcings, prevent as precise a quantification of the temperature changes attributable to WMGHGs and other anthropogenic forcings individually. Consistent with AR4, it is assessed that more than half of the observed increase in global average surface temperature from 1951 to 2010 is very likely due to the observed anthropogenic increase in WMGHG concentrations. WMGHGs contributed a global mean surface warming likely to be between 0.5°C and 1.3°C over the period between 1951 and 2010, with the contributions from other anthropogenic forcings likely to be between –0.6°C and 0.1°C and from natural forcings likely to be between –0.1°C and 0.1°C. Together these assessed contributions are consistent with the observed warming of approximately 0.6°C over this period (Figure TS.10). {10.3}

[!["Likely" ranges and midpoints for warming trends 1951-2010](https://i.sstatic.net/X3sMX.jpg)](https://i.sstatic.net/X3sMX.jpg)

Observed: temperature measurements

WMGHG or GHG: Well-mixed greenhouse gases like CO2

ANT: Sum of GHG and OA

OA: Other anthropogenic forcings on temperature like aerosols and black carbon

NAT: Natural variability such as change in solar radiation
Internal Variability: Estimated lack of knowledge in current earth models

> **Comments:**
> **username_7**: Nice simple answer perfectly on point to the question asked from a rather central source!  Glad you put in the time to add the answer!  

---

