From 127f0307252293f46e1f3997a36868f1d687c5d3 Mon Sep 17 00:00:00 2001
From: Keith Lindsay <klindsay@ucar.edu>
Date: Thu, 2 Jul 2026 15:31:25 -0600
Subject: [PATCH] Update BGC challenge exercises for 2026 tutorial

---
 notebooks/challenge/bgc/bgc.ipynb            | 10 +++-
 notebooks/challenge/bgc/bgc_exercise_1.ipynb | 61 ++++++++++++++++++--
 2 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/notebooks/challenge/bgc/bgc.ipynb b/notebooks/challenge/bgc/bgc.ipynb
index 6e85a9dda..a1405c046 100644
--- a/notebooks/challenge/bgc/bgc.ipynb
+++ b/notebooks/challenge/bgc/bgc.ipynb
@@ -16,6 +16,14 @@
     "## Biogeochemistry in CESM"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "ec18022c-4ae1-404a-8688-f7b265310bfa",
+   "metadata": {},
+   "source": [
+    "### Caveat: Support for coupled biogeochemistry in CESM3 is still under development. So this content describes biogeochemical features in the context of CESM2. For example, resolutions that are referenced are resolutions used in CESM2."
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "34516fd8-ed12-44c0-ba57-b684c1c279cf",
@@ -205,7 +213,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.12"
+   "version": "3.10.13"
   }
  },
  "nbformat": 4,
diff --git a/notebooks/challenge/bgc/bgc_exercise_1.ipynb b/notebooks/challenge/bgc/bgc_exercise_1.ipynb
index e3e910b22..af9310523 100644
--- a/notebooks/challenge/bgc/bgc_exercise_1.ipynb
+++ b/notebooks/challenge/bgc/bgc_exercise_1.ipynb
@@ -5,7 +5,49 @@
    "id": "f406f992-92bd-4b17-9bd3-b99c5c8abaf3",
    "metadata": {},
    "source": [
-    "# 1: Set up a BGC case"
+    "### Caveat: Support for coupled biogeochemistry in CESM3 is still under development. So this content describes biogeochemical features in the context of CESM2. For example, experiments use CESM2 resolutions."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "11d78f47-b7dc-4bc7-af9e-284b010ef2ff",
+   "metadata": {},
+   "source": [
+    "# 1: Check out a sandbox of the most recent version of CESM2.1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "465ba5c4-1a38-4931-ac27-0c1d76627a8b",
+   "metadata": {},
+   "source": [
+    "## Run the following commands in the parent directory of where you have checked out versions of CESM3.\n",
+    "\n",
+    "## Note that CESM2 manages versions of components of CESM with a tool called `manage_externals`, not `git-fleximod`, so the commands below differ from what you've used in CESM3."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "d71a0ef3-316d-4fc9-9989-b0118c0a3936",
+   "metadata": {
+    "jp-MarkdownHeadingCollapsed": true
+   },
+   "source": [
+    "```\n",
+    "cd /glade/u/home/$USER/code\n",
+    "git clone https://github.com/ESCOMP/CESM.git cesm2.1.5\n",
+    "cd /glade/u/home/$USER/code/cesm2.1.5\n",
+    "git checkout cesm2.1.5\n",
+    "./manage_externals/checkout_externals\n",
+    "```"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f0a07ccc-fdee-4bf8-870f-a559401c63c6",
+   "metadata": {},
+   "source": [
+    "# 2: Set up a BGC case"
    ]
   },
   {
@@ -24,9 +66,20 @@
     "<div class=\"alert alert-info\">\n",
     "<strong>Exercise: Set up a BGC control case</strong><br><br>\n",
     " \n",
-    "Create a case called **b_1850** using the compset  ``B1850``  at ``f19_g17`` resolution. \n",
+    "Create a case called **b.e21.B1850.f19_g17.001** using the compset ``B1850`` at ``f19_g17`` resolution.\n",
+    "\n",
+    "```\n",
+    "cd /glade/u/home/$USER/code/cesm2.1.5/cime/scripts\n",
+    "./create_newcase --case /glade/u/home/$USER/cases/b.e21.B1850.f19_g17.001 --compset B1850 --res f19_g17\n",
+    "```\n",
+    "\n",
+    "Create a case called **b.e21.B1850_BPRP.f19_g17.001** using the compset ``B1850_BPRP`` at ``f19_g17`` resolution.\n",
+    "\n",
+    "```\n",
+    "cd /glade/u/home/$USER/code/cesm2.1.5/cime/scripts\n",
+    "./create_newcase --case /glade/u/home/$USER/cases/b.e21.B1850_BPRP.f19_g17.001 --compset B1850 --res f19_g17\n",
+    "```\n",
     "\n",
-    "Create a case called **b_1850_bprp** using the compset ``B1850_BPRP`` at ``f19_g17`` resolution.\n",
     "- What happens when you run create_newcase? Follow the instructions to get this working, but don't do it for real unless you know what you're doing.\n",
     "\n",
     "Run case.setup and preview_namelists for each case.\n",
@@ -73,7 +126,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.12"
+   "version": "3.10.13"
   }
  },
  "nbformat": 4,