Carbon in the Ocean

The atmosphere is not the only reservoir for civilization's emissions of carbon.  This page brings the oceans into the picture.  Over longer time scales, most of the carbn emitted today will end up in the ocean.


 Ocean Acidification: Explained in 60 seconds


Source  WXhift  |  climate indicators: ocean acidification [web + youtube]


Hawaii CO2 in the Atmosphere and Ocean


CO2 in the Atmosphere and Ocean

Source  NOAA PMEL graphic [web + jpeg] | data: mauna loa observatory + station aloha



Ocean Perspective on the Global Carbon Cycle

The "airborne fraction" tells us that most of CO2 emissions into the atmosphere stay in the atmosphere for a long time.  But the atmosphere is a small reservoire for carbon.  About 16 times more carbon is stored on land ("terrestrial biosphere").  And about 60 times more carbon is stored in the ocean (in pre-industrial times before the drastic increases in atmospheric emissions). The ocean takes the most carbon, but the rate of carbon uptake is slower.  The trend we see today in the ocean will long outlast the trend we see in the atmosphere.

At present, just a quarter of CO2 emissions into the atmosphere are absorbed by the oceans. CO2 in the air reacts with seawater and forms carbonic acid that acidifies the ocean.   As acidification increases, pH falls.   Since pre-industrial times, the average pH of ocean surface water fell from 8.21 to 8.10.  As a logarithmic scale, this change equates to a 30 percent increase in acidity.  At the current rate, pH could decrease another 0.3 pH units.  This would make the ocean more acidic than any time in the past 100 million years.  This is a dangerous trends because it is more difficult for shellfish to live, as well as plankton at the base of the ocean food web.


Some takeaways


What does this mean?  It means there are many earth systems that interact over relatively short and long time scales that affect and sustain life in the biosphere.  There is a need to think about global environmental change with the aim of returning stability to the system as a whole.  Approaches like geoengineering can provide temporary relief to undesirable effects of some changes--like warming temperatures on the earth's surface.  But larger issues remain to be seen and addressed.



WOR  The oceans: The world's largest CO2 reservoir

WXshift  Climate indicators: Ocean acidification



Seawater Data


U of Hawaii  HOT Station ALOHA surface ocean CO2 data (since 1988)

NOAA-NCEI  Ocean climate laboratory

NOAA-NCEI  World Ocean Database (WOD)

NOAA-ESRL  About the world ocean database

NOAA PMEL  Ocean acidification observations & data


Links for Deeper Exploration


Student Earthlabs


SERC  Ocean acidification: Too much of a good thing?

SERC  A. The carbon cycle and ocean pH. What's the connection?

SERC  B. Ocean acidification: A risky shell game?


Ocean carbon cycle


NOAA PMEL  Ocean acidification: The other CO2 problem

NOAA PMEL  A primer on pH

NOAA PMEL  What is ocean acidification?

IGBP 2012  Ocean in a high CO2 world

NOAA PMEL  Science and environmental education for understanding and stewardship

NOAA PMEL  Ocean acidification educational tools

NOAA PMEL  Sampling educational tools

NOAA PMEL  Carbon educational tools

NOAA PMEL  ANIMATIONS: OA and aragonite saturation state

NOAA PMEL Carbon cycles in coastal oceans



2015 Media


WXshift Three research tools to unravel mystery of ocean acidity


2013 Video


TEDx TESC  Busch | Ocean Acidification in Washington State



Financial  PayDayAllDay.Com




Niijii Films  About | A Sea Change: Imagine a World Without Fish

Bullfrog Films  A Sea Change: Imagine a World Without Fish



CO2 Monitoring

CO2.Earth mainly features CO2 data from measurements made by two scientific institutions at the Mauna Loa Observatory (MLO) on the Big Island of Hawaii USA: the National Atmospheric and Oceanic Administration (NOAA) and Scripps Institution of Oceanography (SIO).  This is the site of the world's longest, continuous CO2 record of direct atmospheric measurements using high-precision instruments.  The location is near the middle of the world's largest ocean, and near the top of the world's tallest mountain, from its base (McGee, 2017, p. 99).  The Mauna Loa Observatory may be considered one of the best locations on earth for making these measurements.  NOAA notes the following locational advantages: 

"The undisturbed air, remote location, and minimal influence of vegetation and human activity at MLO are ideal for monitoring constituents in the atmosphere that can cause climate change."

~ NOAA-ESRL Webpage


Planetary Significance of the MLO Trend


At present, atmospheric CO2 is rising twice as fast as it was in the 1960s.  You can see the difference in data from the Mauna Loa Observatory.  But the rate of change is essentially the same at every CO2 monitoring station.  In the book CO2 Rising, author Tyler Volk writes:


"Data from Alaska and Samoa fit right in with the trend from Mauna Loa and the South Pole, where monitoring was begun nearly 20 years earlier.  We are witnessing a global phenomenon.  CO2 is rising everywhere, and at about the same rate."


~ Tyler Volk (2008, pp. 40-41)


For stations at different latitudes, you will find differences in amplitude—much smaller near the South Pole and much larger near the North Pole. 


Mauna Loa Links


NOAA  Mauna Loa Observatory

Scripps  Keeling Curve & lesson for long term earth observations

NOAA  Mauna Loa CO2 record


See the "MLO" tab for more links about the Mauna Loa Observatory and other earth monitoring stations.



McGee, M. (2017).  Learning for Planetary Habitability: A Lived Experience Study With Senior Earth System Scientists. (Master's thesis).  Royal Roads University, Victoria, Canada.

Volk, T. (2008). CO₂ rising: The world's greatest environmental challenge (2010 paperback ed.). Cambridge, MA: MIT Press. [MIT Press]




Scripps CO2 Monitoring at MLO


scripps 189wCharles David Keeling of the Scripps Institution of Oceanography started high-precision CO2 measurements at the Mauna Loa Observatory in March 1958.  He directed the Scripps CO2 program, including CO2 monitoring at MLO, until he died in 2005. Keeling's son. Ralph F. Keeling. is now the senior scientist and principal investigator who oversees the Scripps CO2 monitoring program, as well as the the Scripps O2 Program that measures atmospheric oxygen and argon.  Both programs are based at the Scripps Institution of Oceanography, University of California San Diego (UCSD) in La Jolla, California.




Scripps CO2 UCSD  Home page

Scripps CO2 UCSD  Keeling Curve website

Scripps CO2 UCSD  Twitter (@Keeling_curve)

Scripps CO2 UCSD  CO2 Data at MLO and other stations



NOAA CO2 Monitoring at MLO


Starting May 1974, the National Oceanic and Atmospheric Administration (NOAA). started a second, indepement CO2 monitoring program at the Mauna Loa Observatory.  NOAA datasets for Mauna Loa CO2 that start in 1958 incorproate Scripps CO2 data from March 1958 to April 1974.  NOAA now monitors observatory facilities at Mauna Loa.  Pieter Tans is the senior scientist and principal investigator who oversees the NOAA CO2 monitoring program.




NOAA  Mauna Loa Observatory webcam (facing west)

NOAA  More webcams at MLO



Calculation of CO2 Mean Values


Monthly and weekly mean CO2 concentrations are determined from daily averages for the number of CO2 molecules in every one million molecules of dried air (water vapor removed).  Annual mean CO2 concentrations are the arithmetic mean of the monthly averages for the year.

Atmospheric CO2 concentrations are expressed as parts per million (ppm).  This is a shortened and common abbreviation for parts per million by volume (ppmv) as opposed to mass.  The UAR Center for Science Education provides a helpful illustration of carbon dioxide concentrations in parts per million.


NOAA  NOAA-ESRL calculation of global means

NOAA  How CO2 levels are measured at Mauna Loa



Time Zones of Mauna Loa Data


Scripps CO2 data is based on local time in Hawaii, USA, where the observatory is located.  NOAA CO2 data is based on local time in Boulder, Colorado, USA, from where scientists coordinate the activites of its global monitoring network.



Preliminary Publication of Data


Data published within the past year should be considered preliminary and subject to change by scientists based on recalibrations of reference gas mixtures or other quality control procedures.  Adjustments may be made to earlier years for the same reasons.  In the past, changes have been minor.

NOAA started publishing change log and notes in 2008 that provides a record of adjustments and reasons for them.



Mauna Loa Observatory


Mauna Loa Data & The Keeling Curve


NOAA  MLO Monitoring & Research Programs

NOAA  MLO Frequently Asked Questions (FAQs)

NOAA  How CO2 levels are measured at Mauna Loa

Scripps CO2  Keeling Curve Lessons

U of Hawai'i Press  BOOK | Hawaii's MLO: 50 Years of Monitoring the Atmosphere

CO2.Earth  Data sources used at CO2.Earth

San Diego UT  Keelings' CO2 measurements as global warming's longest yardstick

CDIAC  Atmospheric CO2 from continuous air samples at MLO, Hawaii


Mauna Loa Visits & Photos


NOAA  Tour information for the general public

NOAA  MLO photo gallery

Nebraska Weather Photos  A visit to the Mauna Loa Observatory, 2008

Worldview of Global Warming  CO2 reaches 400 ppm (2011 photos)

Trip Advisor  Mauna Loa Observatory (Things to do in Hilo, Hawaii)



xClimate Science Data Sources republishes scientific data.   The site makes important climate data and trends more visible.   CO2Now is not a primary source for data.  

CO2Now features data for the concentration of carbon dioxide in the atmosphere.   The main data source is the National Oceanic and Atmospheric Administration / Earth Systems Research Laboratory in the United States, or NOAA / ESRL.   This is one of two institutions that measure atmospheric CO2 levels at the Mauna Loa Observatory in Hawaii.   The Scripps Institution of Oceanography also has a CO2 monitoring program at the Mauna Loa Observatory.   Scripps started the world's first high-precision monitoring program at the Mauna Loa Observatory.

Climate science data is made available by scientific institutions and journals around the world.  If you are looking for a particular data set, an excellent starting point is the catalogue of data sources at  RealClimate is a commentary site on climate science by working climate scientists for the interested public and journalists.

The CO2Now Climate Sheet


Data current as of January 19, 2014

Climate Sheet posts the world’s most current and important planetary data and targets – together in one place from leading global sources.  The CO2Now Climate Sheet enumerates the chain of causes that are driving humanity’s largest environmental crises – global warming, climate change and ocean acidification.  It also sets out key scientific markers for a stable climate system.

0 tonnes

CO2 Emissions Target

Global CO2 emissions for long-term stabilization of atmospheric CO2

“Stabilizing atmospheric CO2 and climate requires that 
net CO2 emissions approach zero”                    

~ J Hansen et al. 

Source 1:  J Hansen et al via NASA |  Target Atmospheric CO2   |  2008
Source 2:  IPCC  via CO2Now  |   AR4 WG1 FAQ 10.3   | 2007
Related:  TED Talks  |  Bill Gates on Energy: Innovating to Zero   | 2010  

 0 w/m 2 watts per square meter

Target to end global warming

Global energy balance  & the end of global warming x

“Stabilizing climate requires, to first order, that we restore Earth’s energy balance. 
If the planet once again radiates as much energy to space as it absorbs from the sun, 
there no longer will be a drive causing the planet to get warmer.” 

~ Dr. James Hansen

Source:  J Hansen | Conversation with Bill McKibben  | 2010

 0.58 W/m2  (± 0.15)

Global energy imbalance from humanity's GHG emissions  |  2005 - 2010

Source:   NASA  |  Earth's Energy Budget Remained Out of Balance  |  2012  
Also:        NASA  |  Abstract & Related Links  |  2012

Also:        Hansen et al.  |  Earth's Energy Balance and Implications   |  2011 
Also:        Hansen  | Storms of My Grandchildren  p. 102  | 2009 

Excerpt from Earth's Energy Budget Remained Out of Balance:

"A new NASA study underscores the fact that greenhouse gases generated by human activity — not changes in solar activity — are the primary force driving global warming. 

The study offers an updated calculation of the Earth's energy imbalance, the difference between the amount of solar energy absorbed by Earth's surface and the amount returned to space as heat. The researchers' calculations show that, despite unusually low solar activity between 2005 and 2010, the planet continued to absorb more energy than it returned to space."

1.91 ppm per year parts per million

Atmospheric CO2  |  Average Annual Rise  |  1994 -  2003

December Data Only  
Calculations by CO2Now are based on NOAA-ESRL CO2 data (Mauna Loa Observatory) dated January 9, 2014

 2.09 ppm per year parts per million

Atmospheric CO2  |  Average Annual Rise  |  2004 -  2013

December Data Only    The rate of increase for this past decade is higher than any decade since the start of the atmospheric CO2 instrument record in March 1958.   
Calculations are based on NOAA-ESRL data (Mauna Loa Observatory) dated January 9, 2014

More Info:

CO2Now  |  Acceleration of Atmospheric CO2 

8.07 pH

Ocean Acidification:  Average pH of Surface Oceans  |  2005

Average pH of surface oceans has declined about 0.1 units since before the industrial revolution.  This is an increase of about 30% in the concentration of hydrogen ions which is a considerable acidification of the oceans. 

“…world leaders should take account of the impact of CO2 on ocean chemistry, 
as well as on climate change…we recommend that all possible approaches
be considered to prevent CO2 reaching the atmosphere.”

~ The Royal Society (2005)

Source 1: The Royal Society | Ocean acidification due to atmospheric CO2  | 2005
Source 2: Wikipedia  |  Ocean Acidification


100-Year Average Global Surface Temperature for November|  1901 - 2000

Source:  NOAA-NCDCState of the Climate – Global Analysis


Average Global Surface Temperature*  |  November 2013

Source: NOAA National Climatic Data Center:  

More Info:  
CO2Now  |   Global Temperature Update

 172 ppm

Atmospheric CO2  |  Lowest level in 2.1 million years

Source:  Science  | Atmospheric CO2 Across the Mid-Pleistocene  | 2009
More Info:  Science Daily | CO2 Higher Today Than Last 2.1 Million Years | 2009

195 countries

Target of Most National Governments

Signatories to the UN Framework Convention on Climate Change (UNFCCC)

The United Nation’s ultimate climate objective “is to stabilize greenhouse gas concentrations in the atmosphere at a level that will prevent dangerous human interference with the climate system.”  (See UNFCCC Article 2 and UNFCCC media releases)

More Info:  |  112 Countries for 350 ppm / 1.5 °C
More Info:  AFP | Top UN Climate Scientist Supports 350 Goal

Note: In the event that other countries (or the UNFCCC as a whole) adopts a quantified atmospheric stabilization target for CO2 or any other greenhouse gases, it will be posted in The CO2Now Climate Sheet. 

 280 ppm

Atmospheric CO2  |  Pre-Industrial Revolution

Atmospheric CO2 was stable at about 280 ppm for almost 10,000 years until 1750.

300 ppm

Atmospheric CO2  |  Highest level in at least 2.1 million years (pre-industrial)

Circa 1912, atmospheric CO2 levels breached the 300 ppm threshold for the first time in at least 2.1 million years.

350 ppm

Atmospheric CO2 Target for Humanity

Atmospheric CO2  |  Upper Safety Limit

“If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that… If the present overshoot of this target CO2 is not brief, there is a possibility of seeding irreversible catastrophic effects.”

~ J Hansen et al

Source 1:  Open Atmospheric Science  |  Target Atmospheric CO2  |  2008
Source 2:  Nature  |  A Safe Operating Space for Humanity  |  2009
Source 3:  SRC  Ecology & Society  |  Planetary Boundaries  |  2009
More Info: | Science of 350

391.01 ppm

Atmospheric CO2  |  October 2012  |  Mauna Loa Observatory

Data dated November 8, 2013 at NOAA-ESRL.

CO2Now links to source datasets |   Atmospheric CO2 data from NOAA & Scripps

396.81 ppm

Atmospheric CO2  |  December 2013  |  Mauna Loa Observatory

Preliminary data released

Data dated January 9, 2014 at NOAA-ESRL.

CO2Now links to source datasets | Atmospheric CO2 data from NOAA & Scripps

885 ppm

Atmospheric CO2  |  Median Projection for Year 2100

This projection is made in C-ROADS, a scientifically reviewed climate simulator. The analysis accounts for the voluntary emissions reductions pledges of parties to the UNFCCC.  This CO2 level represents a global temperature increase of about 4.5 °C.  

Source: Climate Interactive  Analysis as of April 2013
Implications:  The Royal Society  |   Four Degrees and Beyond  |  2011
CO2Now:  Atmospheric CO2 Projections

36 billion metric tonnes

Humanity's Global CO2 Emissions (including land use)  |  2012

2011 global CO2 emissions are the highest in human history.   They are 54% higher than in 1990 (the Kyoto Protocol reference year).  Global fossil fuel emissions made up 91% of the total.  The Global Carbon Project (GCP) posted data for 2011 on November 19, 2013. 

Source:  Nature Geoscience & GCP  |  See "Global Carbon Emissions" at CO2Now

The CO2Now Climate Sheet

Get "The Sheet" by Email:  Subscribe to @mospheric Post 

More Info:  About The CO2Now Climate Sheet

Email Us: This email address is being protected from spambots. You need JavaScript enabled to view it.

Mauna Loa CO2

  • Throughout this website, references to average or mean CO2 levels for any month or year since March 1958 means data collected by continuous atmospheric monitoring at the Mauna Loa Observatory in Hawaii, USA. At Mauna Loa, the remote location, undisturbed air, and minimal influences of human activity and vegetation are ideal for monitoring consituents in the atmosphere that can cause climate change.
  • The Mauna Loa Observatory is part of the National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL), Global Monitoring Division (GMD) in the USA.  The continuous, high-precision measurement of changes in atmospheric CO2 concentrations was started in March 1958 at the Mauna Loa Observatory by Charles David Keeling.
  • The monthly CO2 reading is the most current and comprehensive indicator of how well we are doing, collectively, to address the root causes of global warming and climate change.

CO2 is well mixed in the atmosphere, so observations of concentrations from a single site like the Mauna Loa Observatory are an adequate indicator of world trends for atmospheric CO2. 


Mauna Loa Observatory

The M




CO2 Acceleration  |

Mauna Loa Science and Wonder  | 

Mauna Loa Observatory, Hawaii  |  NOAA / ESRL

Monthly CO2 Data Since March 1958  |  NOAA / ESRL |  Scripps Data

About the Mauna Loa data  |  NOAA)

Why Mauna Loa data is important  |  NOAA

Atmospheric CO2 from continuous air samples at Mauna Loa Observatory, Hawaii  |  CDIAC 1958 - 2001)

Keelings' CO2 measurements as global warming's longest yardstick | San Diego UT 

Global Carbon Emissions

In November 2021, the Global Carbon Project published its Global Carbon Budget 2021 which concluded:

  • The global average concentration of CO2 in the atmosphere increased from about 277 parts per million (ppm) in 1750 to 414 ppm in 2020 (up 49%)
  • In 2020, global CO2 emissions from fossil fuels were 34.8 GtCO2, a decrease of 5.4% from 36.7 GtCO2 in 2019.
  • For 2021, global CO2 emissions from fossil fuels are projected to grow 4.9% to 36.4 GtCO2, a level which is about 0.8% below the 2019 level. (The 2021 growth of 1.6 GtCO2 is similar to the growth observed in 2010 following the global financial crisis of 2008-2009: 1.7 GtCO2 or 5.5% above 2009 levels.)

Global fossil CO2 emissions in 2021 are set to rebound close to their pre-COVID levels after an unprecedented drop in 2020. Emissions from coal and gas use are set to grow more in 2021 than they fell in 2020, but emissions from oil use remain below 2019 levels.

The record decrease in 2020 emissions was 1.9 billion tonnes of CO2 (GtCO2) [-5.4%], from 36.7 GtCO2 in 2019 to 34.8 GtCO2 in 2020. Emissions are projected to grow 4.9% (4.1% to 5.7%) in 2021, to 36.4 GtCO2. Global emissions in 2021 remain about 0.8% below their level in 2019. The 2021 growth of 1.6 GtCO2 is similar to the growth observed in 2010 following the global financial crisis of 2008-2009 (1.7 GtCO2; 5.5% above 2009 levels).


Annual global CO2 emissions


Annual Global CO2 Emissions
(2011 - 2021)*

2021 Global Carbon Budget (November 2021)

1 Gigatonne (Gt) = 1 billion tonnes


Fuel* (Gt)

Land Use
Change (Gt)

Total* (Gt)
2021  36.4*    
2020 34.8 3.2 38.0
2019 36.7 3.8 40.5
2018 36.6 3.9 40.5
2017 35.9 3.7 39.6
2016 35.5 3.7 39.2
2015 35.5 4.8 40.3
2014 35.5 4.6 40.1
2013 35.3
4.3 39.6
2012 35.0 4.7 39.7
2011 34.5 4.8 39.3

Source data from Global Carbon Project 2021 (via ICOS):
data supplement + global data (.xlsx) + national emissions (.xlsx)

*NOTES: (1) Values for GtCO2 in the above table were calculated by CO2.Earth by multiplying carbon emissions in the linked Excel data file by 3.664, and by adding emissions from fossil fuels and land-use change to determine total emissions

(2) Fossil fuel emissions exclude sinks from cement carbonation

(3) Global fossil fuel emissions for 2021 are projected


Global carbon budget 2021

The data below summarize all human-caused sources of CO2 emissions and global sinks (where the CO2 goes).  Numbers present the yearly average for one decade (2011 to 2020).  Data were published November 5, 2021, in Global Carbon Budget 2021 by the Global Carbon Project.

Global CO2 emissions from human activity

Most human-caused emissions of CO2 into the atmosphere are from burning fossil fuels that had long been stored in the crust of the Earth.   A small part of the fossil fuel total is from new cement usage. 

image: fossil fuel emissions from stack


34.8 GtCO2/yr


Fossil fuel emissions

image: cleared patch of land 


4.1 GtCO2/yr


Emissions from land use change

(mostly deforestation)


Where the CO2 emissions go

From 2011 to 2020, about 55% of global emissions were absorbed by the terrestrial biosphere and oceans.  The remainder were added to the CO2 which is accumulating in the atmosphere.  This accumulation has been observed as continued increases in CO2 concentrations in the atmosphere.

image: blue sky with light clouds


18.6 GtCO2/yr


image: forest floor


11.2 GtCO2/yr

Vegetegation & Soils

(terrestrial biosphere)

image: ocean surface


10.2 GtCO2/yr


(terrestrial biosphere)


Balancing the Budget

The global carbon budget numbers above are the best available scientific determinations at the time they were reported.  Scientists also report an imbalance of 3% (-1.0 GtCO2/yr) between the estimates for global sources and sinks.  See the data description paper, Global Carbon Budget 2021, by Friedlingstein et al for information about the data reporting methods and uncertainties. 

image: fossil fuel emissions from stack


-1.0 GtCO2/yr


(all sinks vs. all sources)



About the Global Carbon Project

The Global Carbon Project and its partners provide annual scientific assessments of CO2 emissions from human activities and their redistribution in the atmosphere, ocean and terrestrial biosphere in a changing climate. The assessments support the understanding of the global carbon cycle, development of responses to the climate crisis and project climate changes ahead.

Assessments and data from the GCP quantify the five major components of the global carbon budget: fossil CO2 emissions (including cement production); land-use change (mainly deforestation); ocean sinks, terrestrial sinks and atmospheric accumulation.  These assessments also provide the best-available quantification of the imbalance between global emissions from human sources and changes in the atmosphere, ocean, and terrestrial biosphere.




CO2 Past.  CO2 Present.  CO2 Future.